Most British people don’t respond well to attempts to cow them. They refuse to be cowed! To allow oneself to be cowed would be cowardly. To do so would have one accused of cowardice, of being a coward.

It’s definitely usable as a verb, see https://www.merriam-webster.com/dictionary/cow

I am not responsible for your incomplete grasp of the English language.

https://www.merriam-webster.com/dictionary/cow

See the second definition.

It’s not a common usage these days, but it’s absolutely valid, though probably unknown to most ESL folks.

> Cow is not a verb

Are you cowed yet?

Well, considering their usage was in fact both correct and perfectly common, and considering that you have set the tone yourself that insulting people is ok by opening with doing it yourself, you surely cannot possibly be anything but fine with it being open season on pointing out how freaking ignorant that was eh?