Some people will always hone in on others weaknesses, it is the only way they can make them selves feel confident.
We all have weaknesses, mine are being fat and bald and when pulled into any form of confrontation these will be the things that will have derogatory terms thrown at me.
You just have to remember that by using your weaknesses against you they are in fact showing there own insecurities and display their inability to form any kind of intelligent form of criticism or helpfull suggestion.
You also have to remember though, that amongst a group of Friends, these same weaknesses will also be a form of humour towards one another.
Right I'm off to get me lardy fat bald ass of to the garden centre with swmbo :(