Social media kids out of control

I watched a beauty tutorial the other day. The make-up guru used a foundation which was 2 or 3 shades darker than her natural skin tone making her skin appear extremely yellow. At first I wasn't sure if she was actually aiming for a tanned look, but then she said her look was inspired by a quite pale celebrity. So I commented: "Your foundation is too dark." and other viewers agreed. But of course not everyone shared my opinion, there was always someone who screamed "HATER!" Yeah. How did I offend anyone? I don't think there was anything hateful about my remark. In fact, it was rather well-intentioned and not personal, if you know what I mean. If I said "OMG! You look ridiculous!", then people might get offended. I'd probably kill my friends for not telling me the truth before my video got uploaded and clicked by thousands of internet trolls. Maybe this foundation also happened to be part of my daily make-up routine and I'd been going out like this for months. So why didn't anyone close to her warn her?