I agree with you in that anyone can show an abhorrent side of beliefs, religious or otherwise, even when there isn't inherently something violent in their subject matter.
Not going to go into discussing the details of Islam as religious discussion is forbidden. I have to ask though if someone truly thinks it's somehow the religions fault that these actions are being done and justified, then how come it's still a very minute percentage of the worlds total population of Muslims?
I've never denied the questionable parts of the Quran, I'm openly gay after all and my family is conservative. I do believe however, that everyone should be free to practice whatever their beliefs or non-beliefs help them make a better person as long as they don't impose it on others. Which seems to be the way the US is going as far as Christianity is concerned might I add.
You're absolutely right that I could denounce it completely, but for me personally it's less about the religion and more about my own culture and community that it ties into. I'd argue that a lot of the major religions also do good which is overshadowed by the negative publicity. While positive influence can be had in a secular manner, some people just need to believe in something for various reasons to get through life, and if it makes them be a better person and contribute to society or help their fellow man then I don't see that as a bad thing.