I observed a growing number of men and women are referring to unmarried men living in their parent's houses are useless and takers of space. This is dangerous language that is often associated with genoc*de. Of course, if you said that about childless and older women you would be banned, even when technically the same logic applies to them.

Does anyone else find this dehumanizing language against under-average men concerning?

Useless men are also still more useful than useless women if SHTF. For example, men without women can learn to cook, keep house clean, and care for their own, so they don't really need a woman in their lives except for sex and being born. On the other hand, women's bubble of independence is only kept by male drones doing shitty and dangerous jobs to keep the basic infrastructure, keep safety and enforce the rights women have. If those men did not have a reason in their lives, such as a family or interest in dating, those men just would do enough for themselves and let everything else rotten (as they should about any unfair system that takes away more from you that what you give it).

It is true those men are not contributing to society, but to be fair society never contributed anything to them. Many of those men are not working, but most are working and earning just enough for themselves. These men are not contributing much to society, but they are not a huge load to it either, unless they are addicts or something. In fact these men keep whole industries of entertainment, sex work and porn alive, which also pay taxes and keep economy running, while they are sedated by those things, so they are not a threat to the system that keep this fake safety bubble that women enjoy so much.

It just bothers people that those men exist, but not for being a load (they are not). They just not want to look at them because it reminds them back that they could at any day be exactly as them, and the fact that people really value you by status and money, and not by being yourself, in fact you are useless as those men for most people if you did not have what it takes to be valuable. Same reason people hate to look at beggars. These men remind us that we are fundamentally worthless and just working bees for a system that does not care about us and never will, just about what we can give to keep it running.

TLDR: It is ironic supposedly useless men in society are openly dehumanized by supposedly tolerant people. It is true these men are not contributing a lot to society, but also they are not a huge load to it. 99.99% of these men are harmless and attacking them is beating a dead horse.