Unable to remove a steam based friend from friends list

I've recently accepted a friends request and soon learned that it was a big mistake. Person has been constantly stalking me and refuses to stop.

This person was added via steam's method of friending in the game. He/She is also the only person that I'm incapable of removing or blacklisting. "Miscellaneous" is grayed out for me.

This has become nuisance and impeding in the enjoyment of playing the game. Is there a reason why I can't remove or block the person? Is there a way to fix this?

I’m having the same issue on xbox. Some feedback on this would be appreciated .