Trolling, at least in its original meaning, is not "spreading misinformation". It's saying things for the sake of provoking anger in other people that you despise or you just don't connect emotionally with. So it makes perfect sense to me for rightwing trolls to excite anger and confusion in leftwing people by appropriating a completely innocuous gesture and using it as a provocation. It doesn't really have to mean anything or to capture or express your true beliefs- the important thing is just that others will go nuts over it.