As a massive believer in free speech, I love this XKCD comic!
You absolutely have the right to say whatever you want (short of the illegal types of speech – hate speech and obscenity or shouting “fire” in a crowded theatre.)
But you also have to accept that whatever you say might be criticized, questioned or even corrected and that doesn’t necessarily mean that your rights are being violated or your opinion is under attack.
(Contrary to this comic, I’d say it also doesn’t mean that you’re an asshole for what you said – it just means someone else disagrees with you and that could be because of anything from a simple misunderstanding to a genuine difference of opinion.)