Think of it like how everyone just hates on mac or iphones etc., it becomes a bandwagon and people just start saying "don't get that" without even knowing the reason. There is a lot of blind hate. In this case, razer do have some problems worth noting, despite most telling you not to get them cos of reasons they don't even know.
Razer keyboards and mice had a lot of problems in the past, and customer service wouldn't do shit, also razer keyboards aren't even using authentic cherry mx switches, they are using a chinese copy of cherry mx switches, called kailh, and claiming that they are better than cherry mx switches. Their marketing strategy and product lineup overall tends to favour looks way too much (chroma everything) and disregard price, making their products a bit overpriced (Tournament edition blackwidow keyboard is an exception of this, one of the cheapest mechanical keyboards out there, but their overpriced products are mainly the chroma products and their headsets).