Not really, it goes withing the framework of freedom to define what actions are to be allowed or not under certain licenses.
There is nothing wrong with making, let's say, a licence that prohibits the use of its adhered product for activities such as the development of nuclear weapons.
To be clear, there is nothing wrong with having political ideas behind what you do, at the end of the day Mastodon was created for political reasons, first, to support free software, second, to create a web alternative to the shitshow that twitter tends to be.
Having that said, enforcing the AGPL rules is an activity that should be done regardless of your political ideas, if someone is violating the AGPL3 the projects have every right to ask them to comply, especially when the offenders belong to powerfull corporate groups that do have the money and the resources.
Mastodon saying "we don't like them" is an expression of honesty IMO, but not the only reason to why they want to seek legal counseling.
I think they are fusing, conservatives and racism have almost always been correlated, so there is a common ground.
Having that said, nazism and republican conservatism are surprisingly different, say, nazis are anti jews, conservatives are anti mexicans. Again, there is a common ground.