You need a really good teacher, because the Koran suggests the use of all kinds of underhanded and direct violence against those who are not Muslim. And this isn't something that was done in the past, only. It is orders and directions for live Muslims everywhere. It's just that most Muslims have natural love in their hearts for all people, and that's why they don't follow the directives, literally, like they are ordered to.
Sure, Islam is good. It is good for this life and for Muslims, but not for anybody else.
It doesn't get EVEN ONE OF ITS BELIEVERS into Heaven. It is a lie in that regard.
This does not address the issue of bad teachers and bad people, of course.
(Part I have crossed out is part I personally cannot agree with. Although I am an athiest, if this belief is wrong I would hope to be judged by my deeds, not by adherence to one or another old book. I would hope the same for those who for cultural, family or any other reason follow one of the many religions.)
Judgment by deeds is the reason why people are lost. NOBODY can be good enough to be saved. Judgment by deeds is only there to determine the quantity and quality of destruction in the afterlife. We all need to find a reason or way to get God to GIVE us salvation, other than because we deserve it. Why? We aren't good enough to deserve it at all.
I'm an atheist, but whatever. Even were I not, I would severely disagree with this. The whole "original sin" argument has never made any sort of rational sense. We are what we are, and only by deeds can we devolve or evolve into something lesser or greater. What you think has no morality, it's what you DO.
The whole original sin argument IS the ONLY thing that makes sense. After all, you only get what was handed down to you from the DNA of your parents. They got it from theirs. And they from theirs, all the way back to the beginning. If it is mistakes in the DNA, then it is ORIGINAL MISTAKES (mistakes = sins).
We are coming upon an age that is able to change DNA. We are even able to change the DNA throughout an adult person's whole body right now. It is a bit dangerous to do. And it needs a lot more study. But it has been done to correct problems in the makeup of certain individuals. One woman had her glaucoma (or similar genetic disease) fixed this way. I haven't followed it enough to see if there are any side effects or not. But it seems to be that we might be able to correct original sin sometime.