I have to say I agree... The comments were ridiculous and blatantly false so no sensible person would believe them anyway, so why waste your time fighting them...
I think IR was a prime target for some bashing, given his record and that bizarre interview he did. And people did start bashing him on SM - but he just completely ignored it all so people soon got bored of that, whereas the family fought back and that gave the trolls the reaction and attention they were looking for. And so it all escalated. Moo.
Eta - I'm not blaming the family for the harassment at all BTW, it's completely out of order and they obviously think that sticking up for themselves is the best course of action.