So what makes it OK that Louis CK is joking about it but it's despicable if Colin does it?
I hate this argument: "Comedian X said it so Internet Personality Y said nothing wrong."
It is all about
CONTEXT: When was it said... How was it said... Who said it ... for what reason did they make the comment... etc., etc., etc.
Comedians make jokes all the time about race, sex, religion, etc. (See e.g., Howard Stern, Chris Rock, Amy Schumer, Sarah Silverman, Louis CK, Stephen Colbert, Kevin Hart, Bill Maher, SNL writers/staff, etc.. etc., etc.). They are considered to be "humorous" because the jokes generally make some sort of social commentary in addition to being funny. If not, those comedians usually get themselves into "hot water" as well (see, e.g. Howard Stern, Bill Maher, Amy Schumer, Michael Richards, etc.)
Just because someone says something, if it comes across as mean-spirited, not funny (yes, "funny" is in the eye of the beholder) or rude, it is going to not be taken well (see, e.g, Michael Richards, Pewdiepie, Colin Moriarty, etc.), it is going to not be received well. And, it matters who is making the comment and what their HISTORY of making other comment is.
It only gets worse when the offenders try to "explain" themselves and justify their comments. Then "defenders" try to downplay the issue and it only spirals out of control, making the situation worse for the person who made the comment, even if that original comment was innocuous.
So, yeah, Colin has brought some of the backlash on himself by not at least showing some understanding of why some people might have been offended by the Tweet. Not that he was wrong for making what he, I guess, thought was a joke or that he needed to throw himself on the ground, show "contrition" and beg for forgiveness, but then he acts completely immature (at least publicly -- who knows about privately with the KF guys) by immediately resigning from KF. He then makes fun of those who criticized the comment (including some of his "friends" from KF and IGN)... Seriously, if you are going to dish it out, be prepared to take it. He has a history of making either not funny or marginally funny "jokes". Yet, he is obviously thin-skinned like so many others who believe that their positions are superior to the opinions of those around them.