Of course you can.
Alcohol users are acting within the law and the standard of behaviour deemed generally acceptable by society.
Coke heads aren't.
I still don't see how alcohol being bad makes illegal drugs ok.
A more logical conclusion to the 'alcohol is bad and and that's legal' train of thought is that alcohol should be made illegal rather than all harmful substances made legal.
Not that I'm saying that should happen, because there is no need for a one size fits all approach.
It doesn't matter how much you go on about alcohol or tobacco, if you freely admit to taking cocaine, most decent people will consider you a low life.