I'd call to ask the receptionist if people actually care about it. If they say yes, just cancel. If they say no, just go and make them all look foolish.
If you're set on a written response, I'd go with "I expect the university and its animal clinic be leaders in the community, and in their specialty. How disappointing to realize that they have fallen so far behind both the science and the community that, instead of leading, they have become staunch holdouts of fear and insecurity. With actual scientists proving the case, even politicians and eventually even the CDC have all acknowledged that masks do no good and are likely harmful. Shed the fear and get with the program. Until you do, please cancel my appointment and remove me from all your mailing lists. Sincerely..."
I'd call to ask the receptionist if people actually care about it. If they say yes, just cancel. If they say no, just go and make them all look foolish.
If you're set on a written response, I'd go with "I expect the university and its animal clinic be leaders in the community, and in their specialty. How disappointing to realize that they have fallen so far behind both the science and the community that, instead of leading, they have become staunch holdouts of fear and insecurity. With actual scientists proving the case, even politicians and eventually even the CDC have all acknowledged that masks do no good and are likely harmful. Shed the fear and get with the program. Until you do, please cancel my appointment and remove me from all your mailing lists. Sincerely..."