You could replace "shitty" with "thoughtless", "callous", "cruel" for example. It's quicker, and more satisfying, to simply use the shorthand "shitty".

Also, what argument? Does the fact that the lady in question did not have anything to defend against, nothing to be ashamed of, really hinge on the exact definition of the shittyness of reddit trolls? Heh. So it's simply a statement. And if you disagree that such behaviour is shitty, make your case. If you don't, I really wonder what we're even talking about here.