The situation is very serious, but I think the most likely way for things to end in catastrophe is to scream that it is genocide, for exactly the reason in the "boy who cried wolf" fable.
The word "genocide" carries powerful connotations, not all of which are met by a permissive reading of the United Nations definitions. Arguing that "technically we would meet this definition especially if activists get the right group added to the definitions"--which is what you're doing--is not really materially helpful in changing the actual situation.
The actual situation is already rather horrible, with trans people already unable to access medication in multiple states in the United States. This is largely (though not completely) because the right has managed to portray trans issues as entirely ideological, helped in greatest measure by none other than...trans advocates themselves!
We generally don't think twice about a goal of eradicating racism or eradicating child poverty or eradicating cannibalism. Getting rid of undesired states of being and/or profoundly antisocial attitudes is generally welcome (though it could still be the case that the methods undertaken are worse than the problem).
However, trans activism based around Queer Theory (in concept if not literally stated as such) is absolutely an ideology. You can't challenge heteronormativity in an ideologically neutral way. For example, "trans women are women" is not a statement of fact but rather an affirmation of how society should construct the two categories: that is, it's an ideological statement. In contrast, "people deprived of hormones (that they take to help manifest a core part of their identity) are subject to severe psychological distress and possibly physical danger and discomfort" is not an ideological statement at all. Neither is, "gender affirming care is the only demonstrably effective way to provide relief to at least a large majority of people with severe gender dysphoria".
The most effective approach to claw back the basic rights that are being destroyed will be to stop presenting the situation as an ideological one and instead as a human one. As part of that, attacking what is framed as the goal of eradicating an ideology ("ideocide" perhaps) using the word "genocide" without making it very clear that this is not about ideology is unlikely to work. Indeed, an apparently ideologically motivated use of the word "genocide" is likely to backfire.
The best counter to dehumanization is humanization, and the easiest route to humanization is to be relatable, personal, and relatively non-threatening. This probably requires putting off some goals of trans activism unless and until there's adequate organic support. But then you don't even need to talk about genocide because dehumanization fails and persecution looks grossly abusive.
(Lambasting Knowles' argument that it wouldn't be genocide to slaughter lots of people if it wasn't about genes is perfectly safe and highly warranted. It's rather shocking that anyone would think to utter such things. It's like arguing that "well, if we flay the skin from our enemies, it's not torture as long as we anesthetize them first and kill them afterwards"...like...what is wrong with you, Knowles?! But mixing up the "I think it's cool to argue technicalities about whether a mass slaughter is genocide!" argument with the "eliminating an ideology isn't the same as eliminating an immutable identity" argument I don't think is a good idea. The former argument can be ridiculed for the transparent barbarism that it implicitly endorses. The latter requires a thoughtful treatment.)