OF-COURSE NOT! after-all, you can't expect everyone to like you. That's just being naive. This is nothing new to Muslims. In fact Prophet Mohammed was verbally insulted soo many times by his enemies, attempts of assassinating him, and even had garbage thrown at him on a daily basis. In fact a women use to throw that garbage on him ...and she was absent one day, and guess what the Prophet did? ... he went to visit her concerned if she fell ill. That was the actions of "the living Quran" as his wife called him.
We are commanded by the Quran to spread the message, as some are ignorant of it. If they continue ridiculing then we must leave them in protest (4:140) as we might become like them. We are judged for what we think and not others, but if we get a chance to present the truth, than we share it.
For me, when people speak bad about Islam and Prophet Mohammed (pbuh) it's an opportunity to educate others and present the truth. I log here almost everyday and I read the most insulting horrible things about Islam and Muslims, and have not killed no one nor believe any of these posters should be killed or even insult them back as a true Muslim, as the infallible Prophet (peace and blessings be upon him) said, can never be a slanderer, a curser, an indecent, or an abusive person.
I mostly ignore the really nasty ones, and sincerely address all the other ones. Many times I don't even report violating post so, people see the stuff we are subjected to. Many Non-Muslims even condemned these posters behavior.