This is inspired by a thread where a theist posted a video that has a biochemist arguing the existence of God.
Do you find it necessary to prove to atheists or theists who believe in other gods than your own that your god exists?
Why or why not?
Not being a theist, I can't answer the question. I will say, however, that unless I want someone else to believe as I do about anything, I should be prepared to give them my best reasons for believing as I do. And this is about any subject, not just God. And that's the whole point -- my beliefs serve to inform my actions, and I've no responsibility to prove myself to anyone.
However, if one wants to do missionary work -- that is, to change the beliefs of others -- then I think one would want to be able to prove one's belief is true. To expect someone to believe something for no other reason than that you do is a bit too sure of oneself, in my view.
Still, it can't be denied that missionaries have done exactly that -- changed the beliefs of others. Never, so far as I can determine, because they had proof of what they believed, and far too often using cruel methods. Read up, for example, on missionary activities in the Indian state of Goa, the persecution of African religions by both Muslims and Christians. Holland in the 17th century was home to many Jewish "Conversos" from Spain, where forced conversion was very real.