The number of "transwomen" is irrelevant.
More than that, the fact the the changes are motivated as being "for transwomen" is also irrelevant.
Anyone demanding free access to women's spaces for any male would get the same objection. It's the policy that's being objected to, not the people proposing it, and not their motivations.
I'm sure those making the demands think they're a benefit for some group, but that group is small, and there are 30 million women who are well aware of what 30 million men are like.
If it was male goths demanding access to women's spaces on demand, then we'd be objecting and we'd be "gothphobic"...
This is not directly about trans people. It's that the policy being proposed allegedly for their benefit causes far more total harm to far more people than it helps.