should anonymous comments be allowed or blocked ?

i currently blocked all the anonymous comments on my site though this was not the case before for past 3 years my blog was open for anons to comment and comments was always positive but recently i got the first shitty crappy comments from an anonymous coward who i think was just visiting my blog to leave his BS behind with cruelty and hatred i really not able to figure it out who is this fukcin, friggin, as**le and airhead was, i really like to warn him that i will not stand for this shit anymore.

and now i came to conclusion that making the anonymous comments block help prevent from link spammers and i believe that it is not much of an inconvenience to legitimate visitors and if some one has something to say which is not offensive then why hide behind their statement?

what ever it is the anonymous coward stopped trolling my site once the anonymous comments was blocked and if he still likes to say something let him tell to me directly not hiding and shivering in the corner.