Successful movements throughout history have often had to align themselves with sworn enemies to advance their cause.
I remember Jerry Falwell explaining in the 80's or 90's how, even though he believed the Mormons and the Catholics were Satanic and not true Christians, they had certain goals in common, plus they had a lot of money, and it made sense politically to align with them in order to achieve said goals.
Similarly, pro-Israel Jews currently find themselves forced to align with Evangelical Christians who they know hate them deep down, but they have a lot of money and influence, and they support Israel for very different reasons (Israel has to exist in order for the End of Days to happen, ushering the return of Jesus to Earth, or some such nonsense).
These alliances with sworn enemies often backfire spectacularly, though, like when the Communists and the garden-variety secularists, along with pro-democracy forces, all aligned with radical Islamists to overthrow the Shah of Iran. Once that goal was accomplished, the radical Islamists took control of the country and executed most of the Communists, secularists, and pro-democracy people en masse. Or when the U.S. aligned with and armed the mujahideen in Afghanistan in order to oust the Soviets, only to have it all bite them in the ass on 9/11.
I don't think it's inherently wrong to seek temporary alliance with your enemies, but you'd damn well better be smart about it, do not forget for a second who these people really are, and have a plan for what will happen after your goal is achieved. The people who are screaming about aligning with the far right are expressing a legitimate fear: that once they succeed in taking down the trans with our help, they will be emboldened and set their sights on taking us down next. Either that, or they will try to take us all down simultaneously, because we're all the same to them anyway (a concept which we've encouraged with the whole "LGBTQ+ community" thing.)
At the end of the day, though, what's true is true, and if some awful people acting in bad faith also happen to recognize a particular truth, that doesn't automatically change what the truth is.