Banning them is no more an option than censoring the Net is possible. Flaming isn't personal. Someone who doesn't know you and hasn't met you can't possibly be relating to you, yourself, your ideas. Don't take it personally. Flamers should never be responded to in kind.
Personal attacks are unethical.
Every civil reply is a victory for free speech, and a small triumph for the freest information culture in the world. People who communicate online have to learn discipline about conflict. The opportunity to argue online is infinite, as is the number of people willing to argue with you. The vast majority of posters on Web sites are lurkers, information foragers, workers, people much too busy, mature or civilized to flame. Accept unfettered criticism.