To Equate the declining of business - to bake a specific type of cake - with the refusal to serve someone on racial grounds, is not valid.
I agree with this. Human rights legislation generally disallows discrimination on the basis of those things that cannot be changed. Whatever the colour of your skin, that is something which you cannot change, whatever your sexual orientation, that too is something you cannot change.
If you have a shop that's open to the public, you have to accept that some of the public that comes through the door may have attributes that you find offensive. But as long as those attributes are things which that person cannot change, you are not allowed to discriminate.
Political beliefs are covered in some provinces, but not the federal government, and there is no prohibition in common law against descriminating based on political beliefs. Even where there is legal protection, I suspect it would be limited. For instance, you may be protected from firing because of your political beliefs, but that protection may not extend to allowing you to harangue the staff in the place where you work.
I also suspect that broadcasting your ability to sexually abuse people based on your position or financial status would not be 'protected'.
As a musician, I am not obliged to entertain anybody. I can pick and choose my gigs. It may cost me in the short run, and even the long run, but that's my worry, not the worry of the law.