Oh, they have reasons. They may not be particularly good reasons, or have much of anything to do with KOS-MOS specifically... but there are reasons. The announcement of more DLC moving forward softens the blow, but petty grievances are amplified when one nears the "end."
Why, I personally found myself quite cross when Bandai Namco was blanket de-confirmed. I can -and did, in private- argue several different points to justify that anger... but ultimately, regardless of how compelling the reasons, the past remains immutable... leaving me with little but my own indignation.
Many people are so toxic because they get too close to their desired outcome. When something else makes a splash, they feel threatened. Then, when another character drops, because they feel hurt, let down, heartbroken. Problem is that they are, unfortunately, HORRIBLE at processing it, and instead lash out indiscriminately.
I suppose my point is: Try not to let it bother you overmuch. The attacks are hollow and impersonal. The people do not care about who you are, or what you want. They only care about protecting themselves, with little regard for how.