At first a handful
‘CCP’ - 
‘illegal alien’ or some variation of it -
‘Death to Arabs’ (edit: it’s not a shibboleth but Israelis can really go fuck themselves) -
‘suicidal empathy’ (popularized by the likes of Gad Saad) -
'purity tests - oh yeah? here’s a pell grant tests a la Kamala
will add more if I feel like it
“Tankie” Never met anyone in real life that used the term but I know if anyone uses it online their opinions aren’t serious or fully formed and can be dismissed.
Off topic but I’m reading a book where the author uses “tankies” to describe literal tank crews and I can’t help but giggle imagining a bunch of red communists pulling up to help fight this sci-fi war
My brother used it to describe Jeremy Corbyn
If they’re using it derogatorily, sure