I think the percieved problem is that the union may be funneling money that is in the union interest rather than individual member interests. There has been problems with union corruption. However, union membership is down globally, so they are less powerful and less a bogeyman than the right would want you to believe.

Also, it should be clear that donations should not be the Max amount times membership, but the Max for any individual member, including any other donations. Collective pooling of resources doesn’t collectively pool legal limits. Or at least, it shouldn’t. That’s the point of the limit.