MOL, I am getting some messages for you
Your deepest wounds are surfacing. This is a healing time. It is a time to be very gentle with yourself so you can then be equally gentle with others.
It's been my experience whenever somebody (myself included) seemingly "overreacts" to an external experience, it is because it is triggering memories of earlier and deeper trauma. Your experience in the store is one of those occasions.
Also, in the Walmart when you commented loudly about the lack of sufficient checkers and the checker told you you need to keep your opinions to yourself. She was, of course, expressing her opinion
One thing I have taken a bloody long time to learn is that nobody is really interested in my opinion about everything, any more than I am interested in other people's opinions all the time. Any time you express your opinion loudly, don't be surprised to have somebody within earshot express their opinion back at you. So the lesson here is to learn to keep your opinion to yourself, unless somebody specifically asks for it. And even then, offer it with care because every word is power and will create a karmic ripple. Treat your inner thoughts and feelings like precious jewels, to be used carefully and shared only with those worthy of them.
You are afraid of the people around you, but your fear reaction provokes their own fears. And then the fear reverberates back and forth. One reason you are afraid is because your wounds are surfacing, so you feel vulnerable. That is a normal reaction.
You mentioned you don't want to be around people any more, which creates a conflict with your desire to be around like-minded people. (A lot of us have been struggling with such feelings lately). Also have mentioned several times you don't have anybody around you (in your neck of the woods) that you can talk to or relate to.
This seems like a time for you to retreat into yourself, to be an introvert, to turn inward, even stay home as much as possible, and keep to yourself as much as possible. To explore your fears, your dreams (nightmares) to completely expose and heal some wounds. To listen to healing music, engage in healing activities, to bless your home, smudge the perimeters of your property, journal your thoughts and feelings... and just rest. Allow the wounds that have surfaced the cleaning and healing time they need.
Namaste.
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I'm glad that you posted this now. Even though it was for MOL, quite a bit of what you say is applicable to my current situation. I'll be trying to put some of the advice about sharing thoughts and feelings into practice this weekend. 
Read Art in America(which inspires me), The New Yorker, my books I got for xmas, and do my art and music.
At Walmart, I was NOT talking loudly. The person who told me to shut up was NOT an employee. An employee would not have been allowed to say anything about their employee staffing.
It was another customer that told me to shut up. And I know that Walmart will never listen to anything a customer says, or do anything about it. They will not change anything.
There was a massive sex discrimination class action lawsuit filed against them and the Supremes said that they could continue to discriminate against women.
I have yet to see a rightwinger come up with a coherent reason for their beliefs. It's all about "faith" and gullibility. They believe everything Fox News tells them, and their gun nut networks. You cannot have a reasoned discussion with them. I went to law school so this is frustrating. All I can do is walk away. They are loud and obnoxious.
I argue with them about the Bible, and I graduated from a Christian university(Presbyterian) with Christian professors who taught very deep religion courses. All the religion professors had gone to Harvard and Princeton, but an idiot who believes everything a half-assed preacher who went to a crummy Bible-thump college says wouldn't believe me anyway.
You have hit it exactly: "treat your inner thoughts and feelings like precious jewels".
Freddie Nietzsche said, "If you value your thoughts, why do you speak them aloud?"
He also said, "What are laws to Sons of God?"
Hubby has a copy of Beyond Good and Evil. He started reading it years ago when he was trapped in a marriage to an idiot and a town full of idiots (tulsa). He eventually got a divorce and ran off screaming.
One of the guys in the book club started arguing with me about the "if you value your thoughts" quote via email. He speaks German and has read Nietzsche in the original German. I was not going to argue with someone who was telling me he was superior because he reads German. So I stopped talking to him. He was the only person I have met that I could discuss opera and classical music with. The people in the book club are shallow.
I have met a couple of people that at first I thought were truly educated but found out later that they hold some very backwards ideas. Like a lady with a math degree, works at a bank, also studied Latin, who believes in creationism but "doesn't want to talk about it".
And another one I met at the junior college where I take my welding class, who works in the front office, and was talking about how stupid kids are and how important it is to get an education. Then she said "Those damnyankees should just stay home." I thought, "OK, she's 150 years behind the times and never got over the Civil War. And I'm one-half damnyankee, my dad was from Northeast Ohio and grew up on the shores of Lake Erie. He came to Texas because he was tired of shoveling snow."
The ones that sound reasonable at first --it's sneaky. Baffles me.
I'm surprised nobody's bombed the local movie theater for showing "Lincoln" this week.
We have 4 outside cats. It's been quite cold for the past week and they stay in the patio at night. I talk to them and pet them. And they don't argue with me. Then I go inside and wash my hands and arms and put benadryl gel on them as I am very allergic to cats and dogs. I wheeze and cough too sometimes. (((sigh)))
So I talk to the cats and tell them they're sweet kitties (even when they crap outside the litter box).
Their names are Figaro(B&W like the kitten in Pinocchio, he's a real beauty), Arabella, Tosca and Faust. You'd never know i'm into opera, wouldja??? 
A bit of selfdiagnosis on the internet, I think I have social anxiety disorder with depression. I'm not shy, never have been, just afraid to speak around people who don't share my values. Put me in the city around artists and classical musicians or theater people, and I'm fine.