I don't think Swat was actually asking if he does drugs.
I say stuff like that to people all the time.
Example: Someone asks me a retarded question, I reply "are you on crack?!"
That doesn't mean I assume they
are actually on crack, it's just an expression.
Meth is known to drive people to do crazy things, more so than pot and your other "standard" drugs that us teens are stereotypically doing 24/7.
If he was actually trying to imply your [ex]friend is on meth, I don't think we need a big hissy fit over it. A simple "no" would have sufficed.