I've never heard of Transhumanism until now.  After reading this article, and doing some quickie research, I have to say I absolutely hate it.  Doesn't make a lick of sense to me given I'm pro-death positivity, and know death from an Anthropological standpoint.  If nothing died the land would become barren, the dead provide nutrient rich mulch that can fertilize hundreds of plants, important bacteria and creatures that live off decay would die out.  Whale Fall is the term used for when a whale dies and sinks to the bottom of the sea, it's carcass becomes a vital habitat and source of food for thousands of ocean lifeforms, an animal carcass (humans included.) is no different.

Imo trying to push and justify negativity towards death only perpetuates an unhealthy fear of an event that will happen to all of us, not only can it hurt people mentally, but it can also make the grieving process so much harder for loved ones.  Death isn't a bad thing, if more people spoke about it openly and constructively rather than treat it like a taboo, it wouldn't be so scary.

I don't mean to be rude, or try to say your views are wrong.  I'm just not the right target audience for that philosophy.  Demystifying death and seeing it a natural, unavoidable event, treating it like an everyday thing did a world of good for my mental health so I can't imagine being anti-death.