I disagree in most cases of 18-year-olds specifically, but even if I didn't, I think you should amend your original post to make your point more specific. It's

I disagree in most cases of 18-year-olds specifically, but even if I didn't, I think you should amend your original post to make your point more specific. It's hard to read it as not excusing his violence to some degree based on the comment you were replying to, even with a generous reading.