Donation buttons are donation buttons. Once someone adds one, it's up to the prospective consumer to weigh the values and explore possible misuse of funds and report such abuse to the proper authorities. Add the button and see what happens.
Intellectual property rights of any PUBLISHED courses: you basically have none unless you wish to take it to court and establish them.
I'll remind everyone that copyright law is not entirely enforced in all cases, in fact in very few cases, only certain ones rise to prominence and it takes a lot of money to press your case or have a case that a lawyer would take pro bono or on the contingency of a good outcome paying for their fees.
Respect for "unofficial" personal property rights and designers. This was a bit lacking in the primary exchanges. The acquiescence of the OP author to finally and simply respect the wishes of a designer to remove their work form their site came a little late from my point of view. Being someone watching from the sidelines the progress of the site in question, I am not very encouraged by the style and execution of the provider with some members of the community and communications between the two. Your going to have to improve your demeanor and frankly your professionalism and communication style to capture my interest.
If I ever get to designing and publish a course, you can of course place it on your site and you will not here a peep from me. But if I requested that you remove them for your site, my expectation would be you would do so willingly and gladly to ensure proper community relations, without any form of push back. If you refused I would just walk away, shake my head and carry on. Your site would simply drop off my radar. To be sure your site would not get any good or free press from me at this stage. In fact it might get some bad press. Fortunately, there is always room for improvement and hopefully some lessons have been learned here.