People who have followed court cases and regulatory actions and policy developments in ANY area of law, understand there is often a sort of uneven path that is carved out, often case-by-case, until an area of the law is considered “settled.”
And all of us understand that even “settled” areas of the law are subject to change at times, whether because of slightly different facts, new legislation, tweaks in a constitution, and development over the decades in case law and  politics, to a lesser degree. (Remember slaveholding was “ok” according to our courts at one time, now, with changes, slaveholding is not “ok.” Pollution and spewing industrial wastes and toxins in the air or land or water, once almost seemed to be a sort of property and business right according to some court decisions, without a lot of enforcement or control over the activities–now many such activities are regulated or prohibited in full or in part.)
In several courts around the country, both federal and state, judicial opinions have supported the notion that discrimination on sexual orientation and gender identity is, in essence, a form of sex discrimination, and so if laws and rules about sex discrimination apply to the situation, so too might discrimination because of one’s orientation and identity. This is good news for many in the LGBT community.
In the vastest oversimplification around, my own, and not other thinkers on the topic, it’s the concept of “you don’t fit in” or “we don’t do that here.”  When woman first started working in the trades, or as cops or firemen–there was a lot of pushback, just as there was when women in college wanted to have competitive sports teams and opportunities to play.  The law and policy worked their way around the issues–and while it might still be a bit unusual to find a female construction worker on the job–she’s probably gonna find her employment rights protected provided she can do the job .  When men started to go to school for nursing and enter the work force as nurses in greater and greater numbers, they too faced pushback–they didn’t “fit in.”
In some ways, just as we might have thought it wasn’t smart or “right” for a woman to do this, or a man to do that, the law has shifted, and the more prominent notion is “can you do the job?”  And doing the job usually has little or nothing to do with your race or religion or sex or age (nor frankly for a good number of jobs is your size a factor–Michigan has protections for weight and size–if folks are discriminated on those factors, they might be able to bring a legal complaint about such discrimination too).
And, in what should be good news of sorts for members of the lgbt community–doing the job, or renting an apartment, and so on, should not be hampered merely because you are in the lgbt community.  An article from the Detroit Free Press about some of the developments can be found here:  https://www.freep.com/story/news/local/michigan/2018/05/21/civil-rights-lgbt-discrimination/630297002/
The arguments about sex discrimination and sexual orientation and gender identity having a common genesis, and arguments that both forms of discrimination should be illegal in most instances, is not a brand new one–I made such an argument as early as 1985 on behalf of an individual substitute teacher fired by the Gobles School system (in Van Buren County) and you can find a synopsis of sort from 1994 and 1995 here: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2248257
Mind you, there is still some debate about the issue, not all circuits quite agree, and nods one way or the other by the executive branch of the US can change as well….but in the process (and it IS a process) of puzzling out what is legal or fair and just, changes can and do occur.  This last article may give you more info to chew on:  https://www.natlawreview.com/article/second-circuit-rules-anti-gay-discrimination-sex-discrimination