If you want to support just Firefox, and not the other Mozilla initiatives, there's no way to do that. People reasonably do not agree with the other things Mozilla spends their money on.

That's the Mozilla Foundation. Firefox is developed by the Mozilla Corporation, which is a for-profit entity wholly owned by the Foundation and with separate funding. In fact millions of dollars are transferred from the Corporation to the Foundation in royalties every year. Donating to the Foundation does not fund Firefox development!

Donations went to paying Mitchell Baker millions of dollars per year, and all the other execs.