Because Trump supporters (which the asshole you replied to is, just look at his post history) have been instructed to ramp up their brigading in these past few days, probably has something to do with the G20 summit.

I was just talking about this a couple days ago; you can see it all over reddit, whenever the topic allows for it -even tangentially- they'll flood in and parrot the same tired, prefabricated talking points they've been told to recite and spread outright lies, argue in bad faith (a majority being basement dwelling neckbearded 4channers, they've got plenty of time on their hands to vandalise comment sections), and downvote opposition opinions en masse.