Why do I say that Islam is an evil religion?

[The Grand Nudger]

So?  Honestly, so what if many people disagree?  You know what I use the term evil to refer to, and so...whatever opinion you or the housecat may have on the matter, there either is or isn't malice.  Could be the case either way, like I said.  The basic difference between doing a bad thing, and an evil thing.  

Okay, you think the act of being unfaithful might be a bad thing... why, according to moral realism ? and what's the difference between bad and evil?

I already answered both of these questions, the latter right there in the bit you quoted...... Mind you, in a realist understanding, it doesn't matter what you put into any given category, it matters why you put it there. The statement either does or does not report a fact. I could conceivably call a thing evil, because I feel a particular way about it, maybe it's close to me (as you imagine the issue of a cheating spouse will have any given woman plotting murder as they apprehend a moral monster, lol) - but that's not my position on the morality of it speaking, if so, that's just my emotional investment compromising my rational agency. Sort of like how you get worked up when I shit talk your imaginary friend. Doesn't really make sense to let it affect you the way it does..but you can't help it.

Of course I do. Any person who considers themselves a theist would not agree with or even tolerate moral realism, we think disobeying a supernatural being is a very evil act; this obviously contradicts moral realism.

All you're saying there, is that you believe that there is no objective reason or explanation for why disobeying a supernatural being is an evil act.  Is that what you believe?