It's a lovely relationship. There are different kinds of love and they do love each other. So they are not having rampant sex - so what. It's fine.
If MB is 'allowed' to see men on occasion, which someone has only 'heard' and now gleefully spreads around as if it's gospel what's even the problem? It's not illegal, presumably these people want to see him so that's his sex life sorted.
I am surprised at the nastiness to two innocuous and decent people. The fact that MB might have (and certainly must have had in the past) problems stemming from his accident deserves some consideration.
MB or CM do not have to be ambassadors for someone else's agenda. This is bullying behaviour and homophobia has many forms.