Probably, or maybe they are just repeating what they have heard. It is likely based on simple ignorance of reformed theology and not actually knowing any real Calvinists...or maybe they have known 1 or 2 and those people actually ARE MEAN. Or they have had Calvinism explained to them as "God created sin and punishes people for doing the sins he makes them commit." If you heard Calvinism explained that way, you might think it was absurd too.
Remember that all of us are rude and mean spirited at times, remember how you referred to their "ridiculous rituals"? Would that be considered rude if you said that to a Lutheran?
"A soft answer turns away wrath." Most people who are that argumentative are used to being argued with, or responded to in anger...its the only way they know how to communicate. Usually, being rude in return to a rude person teaches them nothing.
I would not necessarily advocate simply staring at them in silence, that would be kind of weird, but being intentionally kind in a response would be a good start.