The elephant in the room is that Islam is fundamentally and irreconcilably offensive to Christians because they say Jesus was not the son of God. There is nothing more blasphemous than denying this fundamental tenant of Christianity.
If we follow this logic Christian's would be perfectly justified in beating up any Muslim that they happened to come across.
Hang on a second. I understand why you're saying this; it's a common misconception.
The Bible teaches that the world--non-Christians--will mock Christ and his followers (1). That's the expectation, and in the face of this knowledge, the Christian is also called to turn the other cheek (2). Christianity is offensive to the world, but the response is not supposed to be in kind. The Christian is supposed to respond to violence with blessing (Romans 12:20). You may argue that you have not seen many Christian behave this way. I agree with that, and I think it's a very sorry thing when people who claim to be followers of Jesus don't really respect his teachings. I'm sure there are many who claim to be Christians who aren't really, but please also understand that no Christian is perfect either.
So, is Islam blasphemous to Christianity? Sure. But it's also exactly in line with the way the Bible describes non-Christians. Islam is not surprising to, or should not be surprising the Christian.
And no Christian would ever be justified in beating up anyone, including Muslims. The logic really doesn't follow, especially if you know what is in the Bible. I'm sorry the ignorance of many has led you to believe that violence is the logical conclusion, though.
(1) This is all over the New Testament. Like Matthew 24:9, "Then they will deliver you up to tribulation and put you to death, and you will be hated by all nations for my name's sake."
(2) Matthew 5:38-42: "You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’ But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also. And if anyone would sue you and take your tunic, let him have your cloak as well. And if anyone forces you to go one mile, go with him two miles. Give to the one who begs from you, and do not refuse the one who would borrow from you."