Warren is a great name! I thought you were going to say the name was something really odd or wacky...but Warren seems pretty "normal".
I have cousin named Warren actually.
We never tell people the babe's name till after the birth...we'll tell the initials and the sex, and we come up with a silly nickname (DD1 was "bubba" and DD2 is "roro") for people to use, but we figure any name will be loved once the babe is in their arms and no one will be complaining about the name at that point!
I'm sorry people are being so annoying about this though...maybe stop telling at this point and for people who do know (and don't like the name) simply say that it's not something that's open to discussion?
ETA- according to the "behind the name" website, Warren has been in the top 1000 US boys names since 1900! And it's been in the top 400-500 for the last 10 years or so. So it's totally not as out there as some names.