Well, there was a time when i used to keep long beard with no moustache (coz i thought it was cool. Also it helped me feel religious at the same time) but people around me used to assume i'm a muslim. Some of them even said that i should shave it off because to them muslims are all terrorists. That used to make me mad.
First of all, just because a few of them are into terrorism, doesn't mean all of them are bad. Secondly, a beard like that, is sported by people of other faiths too, like the Amish. People should have boundaries and stop telling others what to do.