I am very, very sorry for your loss.
Having lost twin girls myself though, less than 8 weeks ago, I am sorry, but I do think YABU. I also think it's probably understandable though. (and please believe me when I say that just because I have also lost a child, it doesn't mean I think I know how you feel).
I don't think anyone is 'working hard to be blindingly insensitive'. Very, very few people would be deliberately insensitive. Most genuinely do not know what to say, but I suspect feel the need to say something and somehow try and 'justify' what has happened. Others do avoid either speaking at all or mentioning the lost child, IME, but I seriously doubt any of it is done out of spite or deliberately.
I know myself I wouldn't have known how to deal with it if a friend lost their child, and maybe even still wouldn't. I know several people who lost their husbands last year (Afghanistan) and now realise I said consistently stupid things to them in an effort to just say something.
I can't imagine how hard things must be for you right now, but that doesn't mean things are easy for others.
I simply try and understand why people behave and say the things they do, and I have to admit, I have even been able to laugh at a couple of truly ridiculous, and if I wanted to take it that way, hugely insensitive, things people have said. If I didn't, what else would I do?!
People genuinely mean well.