To lump Christianity in with Islam is ridiculous on its face. With all due respect, you obviously know very, very little about Christianity.
I can tell this simply by your statement "Oh, the modern Christians are good?" All true Christians understand that NO HUMAN BEING IS GOOD. ALL human beings, whether they've received Jesus Christ or not may occasionally do good things but all of them, ALL of them are sinners by nature and as such NONE of them can escape hell without true faith that Jesus died for ALL of our sins. So your argument that simply "being good" does not absolve Christians of wrongdoing misses the point entirely. It's not about "being good", it's about receiving Jesus Christ as your savior and attempting to live a moral life according to God's word as much as possible, all the while understanding that you cannot ever actually be completely free from sin. Only Jesus was able to do that.
Islam is completely different. There is no savior in Islam. The Quran compels Muslims to either convert, enslave or kill all non-Muslims. Pursuit of this goal by all individual Muslims is the only way to salvation. By contrast, there is no mandate that Christians forcibly convert non-Christians in the Bible. Where that happens or has happened in the past it is and has been, misguided.
You don't have to agree with me, but to have an honest debate you have to understand the fundamental differences between Islam and Christianity. MORE importantly, you need to understand that Christians have only committed horrific acts only when:
A) They were only POSING as Christians, but in their hearts were actually pagans;
or
B) Were ignoring the word and will of God.