Was the waitress' reaction disrespectful or am I easily annoyed?

She was rude and you have a right to be offended. As a former waitress, I know that it is essential to put all personal opinions aside when waiting on customers. It's not the servers business to know why you eat the way you do. It's their business to take your order and keep their mouth shut. I surely hope your tip reflected the poor service as the waitress surely deserved a lower amount.