Its not a white trash thing. As has already been mentioned, Robert DeNiro’s character wears one in Raging Bull. In the scene near the beginning of the film where his first wife is cooking his dinner, he wears the classic wife beater. Oh and if you haven’t seen the film then rent it - its worth it.
It seems to me most of the pond-life on COPS dispense with any form of clothing on their upper body, except for the basball cap and mullet of course. 
I have a vague memory of doing this before, but maybe at another board.
I almost certainly remember Clark Gable in a movie wearing a “wife beater” type of undershirt. From the 30’s if I’m not mistaken.
This is not to be confused with Gable NOT wearing an undershirt in a movie, and being accused of “killing” the undershirt market.
I have actually been “informed” that, as a guy, any tank top I wear is a wife-beater…tank tops, apparently, are for girls. I told the girl who mentioned this that I thought it was ridiculous, and she seemed to think I was just not keeping up with the latest fashion trends. Which is true, but I still think it’s ridiculous.
The muscly types at my gym don’t seem to know this, and I for one am not going to advise them otherwise.
I’ll probably never wear one of these garments now. That name just leaves too much of a bad taste in my mouth.
So wife beater tops arent t-shirts? I always thought they were ripped yucky old t-shirts.