As a medical professional, there are often decisions you make that are difficult and at times the choices you make can appear cruel, or even heartless but you do the best you can with the resources and the knowledge that you have.
Firstly, an older article on the costs of blood screening, these are for tests that they already have and know what to test for:
https://www.texmed.org/Template.aspx?id=754The health system in America is broken - there are no buts about it. Money plays way too much of a role in the system and the choices made due to that fact can be draconian.
Not taking openly mutant blood is as much about cost as it is about prejudice, although I do believe there is fear involved.
It is much, much easier to simply say 'We will not allow mutants to donate' then it is to fund research into new blood screening that will take into account the huge variance of possible mutations and how their blood might interact with that of a recipient.
I am not saying the decision by the Mayo clinic is right, or fair, or helpful in any way. I do not excuse the results of fear, even if it can be warranted. But there is more then just one side of this story. Do not blame the people on the ground for these decisions. They have a job to do just as everyone else does. If you must protest, then protest where it's needed, at the executive level, at the Government level.
Or go into business and design those new blood screening tests and then offer them to the Red Cross and other donation places for free.