Um, I think only a very very tiny percentage of people seriously say "Die cis scum", I am pretty sure everyone else just uses it to mock Tumblr users or are just a troll pretending to hate-cis. I never came across someone who was serious about it.
Cis is not a slurword, it never was. It just another word for "not trans". People may try to make it sound bad, but most of the people tend to be dumb teens. I have however come across people who were called cis, not in a offensive way, but they end up getting offended.
Also using "normal" is also problematic. It dehumanizes trans people. Like I am not forcing you to use cis but please do not act like trans people are some sort of abnormal monster.