Absolutely not unless you weigh something like 400#s. Cranks have to be strong enough to handle strong or heavy riders standing when they climb a steep hill or sprint. They're built to handle this with ease, with plenty of reserve strength.

It might be a problem if an adult stands on cranks or pedals made for a child's bike, but anybody that tells you not to stand on your cranks might as tell you that riding the bike is bad for it.