No one is getting heated about anything. You just don't seem to understand that unless you said to someone "I'm not selling to you because you are a gay black man", then a buyer can scream discrimination all they like, but they can't prove anything. It wouldn't get past a single lawyer visit, let alone ever making it to court. 

No, there are no legal raminfications in refusing to sell to someone, unless you choose to make it so, by stating the above quote.

I have blocked people because they contacted me after not being happy with their item and that I was discriminating against them because they had a disability, they were a carer, or their child was autistic. Excuse me? How the hell would I know who they were! They can accuse all they like, but unless I know them personally, how am I supposed to know? It also makes no difference. In fact, people playing the disability card get my back up.

If they want to play disability, come to my house where something as simple as having a shower could drown Mr Tippy. He can work, drive a b-double, go camping, but even consider going swimming or having a shower, that could kill him. Any seller I buy off would never know that in a million years. There is nothing in my name, username, location, or the items I buy that would ever indicate there was an issue.