Everyone has the right to adopt and support their particular causes and positions. And, yes, they can even donate millions of dollars if they've a mind to.
But, what I don't get, is why a fast food retailer (operative term: retailer) wants to intentionally alienate a large piece of his potential business. This doesn't make much financial sense.
I guess he can choose to damage his business if he wants to. Adversely impacting shareholders, stakeholders, and investors - that's another story.