I’m pretty sure that it’s not the politicians being swayed by the yobs or the general disdain for Tory supporters but rather those who voted Tory or are more right-leaning (often because of the media scaremongering but that’s a different topic…) but are potential labour voters who understandably don’t like being called scum/nasty/etc.
To me it just switches them off and means that the better arguments aren’t heard.
Of course, there’s negative behaviour on both sides but it seems to me that the lefties tend to be called naive/stupid/soft/etc which are less harsh than the right wingers being called scum, selfish, etc.