I'm going to cut funding
Why would you cut funding?
The AIDS foundation is not doing enough
If you think the charity is being mismanaged then it's probably best to cut funding. Otherwise they could just keep bleeding money.
Maybe that's true, but what is clear is that I don't care about AIDS.  I want the money for other things.
Since this is your own money that you were donating, you certainly have the right to decide what to do with it.  If you are not interested in funding the AIDS Foundation, then you can stop at any time, though it might be a good idea to let them know in advance if this was a large donation.  I hope that you find another charity that you care about, and donate to them.