In a literal sense it can mean being unable to distinguish tone in music. In a figurative sense it can also mean failing to recognize the
tone of a discussion (for example, making a joke at a funeral could be said to be
tone deaf). While I disagree with miaasma's argument, they're use of the idiom is correct.
you are both wrong
this is a really silly discussion to continue to have in this thread but you all seem determined to keep it going, so whatever, i guess i'll bite
my use of the term "tone deaf" pertains to the idea that the inclusion of homosexuality in media is an agenda whereas heterosexuality being entirely ubiquitous is not, a bias often held by straight people who are unable to reflect on their own experience in society being catered to massively, to the point where they react poorly the second another group is treated similarly to them (homosexuality being shoved "down your throat" whenever it's even briefly mentioned in a video game, for example)
this leads to people saying things like "bioware has an agenda for pushing forward-thinking in their games", something you really have to have no self awareness to type unironically, instead of simply realizing that they are one of many video game companies who both realize that we do not live in a world in which heterosexuality is or should be normative, as well as the fact that many people who play video games are not straight. the argument you are disagreeing with doesn't exist
as for your own examples:
i'm no expert on medieval europe's racial demographics nor its density of LGBT people (all i know is that sodomy was punishable by death, but hey, stuff like that doesn't mean gay people just didn't exist), and maybe you are, but either way i'm not sure either of us is in any position to decide what amount of diversity is forced, even in these instances, since conceivably you could write from an angle which depicts these groups during this time period
i agree that context matters, which is why i'm a little perplexed by your statement that half a cast being people of colour or LGBT is "slanted", even today, considering how much media that currently exists fits those descriptions (sometimes at the same time!). if nothing else, i would say this reveals a personal bias, rather than being a reflection of society at large
which leads me back to my point about the term "forced diversity", it being that more often than not, it is used not from a critical lens but from that of a personal bias