The problem is that the terrorists are right about islam.
So what do you think about your prophet doing the same ? Are you also ashamed of that ? He had the mother of 5 children murdered for opposing him. As you (should) know, this is far from the only instance of such action by "the prophet".
I am sorry but unless you wholeheartedly condemn this kind of killing, whoever did it, your gesture means little. If you don't condemn your prophet, when is killing for insults allowed and when is it not becomes a valid question.
To put it bluntly : if you don't condemn this, you're at least somewhat of a terrorist supporter. If you do, how can you be a muslim (given what the daily prayer says, mohamed could not have done anything wrong, plus you'd be lying when you say that prayer).
http://en.wikipedia.org/wiki/%27Asma%27_bint_Marwan
Allow me to put up the full actions of the prophet :
Upon hearing the poem, Muhammad then called for her death
in turn, saying "Who will rid me of Marwan's daughter?"
Umayr bin Adiy al-Khatmi, a blind man belonging to the
same tribe as Asma’s husband (i.e., Banu Khatma)
responded that he would. He crept into her room in the
dark of night where she was sleeping with her five
children, her infant child close to her bosom. Umayr
removed the child from Asma's breast and killed her.
This is far from the only time that muhammad did this sort of thing, and this is part of the "canon" of islam. It is also law in over 50 countries.
Source: http://en.wikipedia.org/wiki/%27Asma%27_bint_Marwan
(but if you doubt the quote, just type it into Google)