The simplest term is hater. Biased or bigoted will also serve. The underlying flaw is ignorance. People are one common species, whose emotional and logical processes are, by nature, exactly the same.
Culture is ‘50%’ (half nurture, half nature) and can generate enormous conflict: “Those atheists eat a dead man,” was that average Roman citizen in the First Century thought about Christians. For one, Atheist because they denied every single Greek and Roman god. The other part had to do with communion: eat this bread which is my body and drink this wine which is my blood.
When you find yourself actively hating someone you meet casually just as soon as that person turns out to be a member of the ‘wrong’ religion, you do these things:
Bite your tongue
Learn what it is about this religion that you hate, and why it isn’t universally despised.