Sometimes, when I go out, I like to drink a lot (ish), and sometimes I don't. It really just depends on my mood and the circumstance. The one thing I cannot stand, though, is someone commenting on how much or how little I'm drinking, and my standard line to anyone that comments is, 'what are you, the drinks monitor?' That usually shuts them up.
I don't think you should ever be bullied into drinking more than you are comfortable and people that do that might just have a problem of their own.