So I created a website which helps people understand what the MMPI is used for. I've been contacted by the copyright owner and asked to transfer the domain over to them. They are claiming I'm infringing on their rights by merely mentioning their trademark (mmpi) but I believe it to be "fair use". What do you guys think?
If: a) people don't confuse you with the trademark holder, and b) you're (hopefully) not making any hint of commercial use (e.g. ads particularly of competing products/services) in the domain name's web site, then you
probably have a fair use. Alas, fair use is best determined in a court of competent jurisdiction if it ever reaches that point.
Perhaps the remaining question here is how far you and/or the trademark holder are willing to go to defend your respective positions. If you really want to defend your usage, then you best seek an actual lawyer with real-world experience in this matter.
Good luck.