No, it's exactly the other way around: if the comment had omitted the first sentence, it would have been fine. That bit could be taken out without any loss of information, and should have been.
Despite how much you've posted about this, there's no serious argument here. A slur followed by a factual statement is obviously still a slur.
As for "shutting down the discussion", that's a bit of a stretch with 650 comments in one thread and 500 in the other.
I think you'll agree that giving a charitable reading to what a person says is the best way to have a clear discussion. While that first sentence, taken by itself and without context, could possibly be interpreted as a bigoted or racist statement, in the context of the whole post I took it to mean "Islam has a reputation for violence, but this reputation exists in part because adherents of Islam in the West support violence more than the rest of the population". I don't think I am going particularly out of my way or being overly charitable in reading it this way. Moreover the grammar "X spoils the reputation of X" is not harsh language, nor is it a tautology - it can be proven wrong. Therefore, I don't think this was an inappropriate comment. How am I wrong? If you bother to answer, please be specific.
That said, I don't fully agree with the statement, actually, as I already mentioned. If you look at support for violence and religious law, etc., in places like the US and Germany, it looks like Muslims do not support that stuff any more than the general population, or they support it less. But looking at the data for France OP might have a point. But, I don't know if he meant only France, or Islam in general, or what, because he never clarified. Maybe he didn't clarify because he stopped reading, or because he doesn't care, or because he realizes he's wrong. Maybe after elaboration he would have outed himself as being a simple Islamaphobe who cherry-picks facts to justify his bigotry. We'll never know that now. But, he also may have stopped posting because you inappropriately called him out in this thread before giving what he said due consideration.
Emotions were probably running high at the time as it was shortly after the attacks and so what you did, in that case, is actually quite understandable. Even if I think you were wrong here, I don't hold this one against you at all. But as the moderator of HN I have seen you time and again shutting down discussion because you perceived something that wasn't there. You are making HN into more of a boring echo chamber and that's sad.
> there's no serious argument here
That's a pretty ridiculous opinion to have considering the voting in this thread. Even if you're right, I'm clearly far from alone in thinking that what you've done here is wrong. So, in fact, there is an argument to be had here, and trying to preempt discussion like that just shows a false and unjustified confidence in your assertion. A little humility goes a long way, you know?