If the individual(s) who responded to your tweet did so should apologize for it. They should have just asked for a bug report and respectfully requested that security issues be reported to the organization before making it public for bad actors to use. Although you are free to post about it however you feel is best.
As far as speech goes, there's a big difference between FREEDOM TO SAY WHAT YOU WANT and FORCING OTHERS TO ALLOW THEIR MEDIUM TO BE USED. That's what XKCD is saying.
If I own a microphone and you want to use it to say something I don't agree with, I don't have to give it to you just because you are free to say what you want to say.
If you want to praise Nazis, racism, bigotry, or whatever, you are free to do so. But you can't expect people to be forced to hand over their platform of communication for you to do it, whether it's a conference presentation slot, hosting servers, social media site, etc.
The government can't make laws preventing you from saying what you want to say. But it also won't make laws forcing anyone to enable you to say it.
As for the argument about show creators who are "forced" to censor certain jokes or statements, again, they are requested to do so. They don't have to do it, but the networks don't have to continue funding the show.