Kinda seems like some people took that 'kids' thing a little too personally, to me.

When tanking, a DPS running off to pull things ahead of you is sending a signal that they think you're tanking/pulling too slow. Sort of a gaming body language. It comes across as rude, regardless of your intentions, so it's good to communicate up front what your intentions are rather than wait for someone to get cranky with you because they're assuming you're being impatient.