Free speech does not grant you immunity from criticism.
I don't mind criticism if it is an honest attempt to foster good discussion of the topic at hand (and it helps if it is articulate and intelligent too).
If, however, all you want to do is name calling and insult hurling because someone dared to disagree with you, then that's nothing more than an attempt to effectively shut the other person up just because you disagree with them. It's saying "I'll censor you by attacking you until you relent and don't say anything more". It's juvenile and pathetic to do that and it shows you have no ability to actually have reasonable discourse with anyone who doesn't agree with you.