Thanks for this question, jlpark.
I feel this is very much to the point. I respond in a variety of ways, none of which is perfectly appropriate or effective.
First reaction is annoyance. "What right does he/she have to push stuff down my throat, as though whatever I accept or don't accept is irrelevant?"
The second response might be to try and put him/her in their place. A fight-back sort of reaction. It rarely has any positive effect.
Thirdly, I can try to get behind the scenes and find what is driving that person to have such an arrogant and judgmental attitude to me and everyone else. Is it their mental health that's driving it? Do they have a hermit-like existence, shut away in a basement, where the only connection with the world is via the Internet? Is he/she disabled, like in a wheel chair, or blind, or deaf..... or even in prison?
If it turns out to be any of the above then this can ease my reaction somewhat. I develop a bit of empathy or sympathy with them.
If the Believer is absolutely immoveable, unwilling to even consider my opinion as reasonable, then I call it quits and can be quite forthright!
In the final analysis, what does it matter if we disagree. There are some much more vocal people with better gifts in expressing themselves without holding back.... lol.