The evil is definately superimposed but it's also intrinsic, as soon as someone says that only my way is the right way, everything else follows.
Again, where's your evidence?
It's not even remotely evil for people to disagree or feel right.
What's more, the 'superimposed' evil (which you readily admit to) was largely from
secularat the very least non-Christiansociety, such as the concerns of running an empire, building wealth, etc. All sorts of stuff that had nothing to do with Christianity before Constantine got it wrapped up in Rome.
Right now your claim that "[l]eft to their own devices, religions would be as primitive and destructive as extreem Islam is today" is looking like a pretty good load of nonsense.
Love your enemies!