What is the likelihood someone will be fired because they're in a heterosexual relationship versus someone who may work for a company or an individual whose views aren't kind to homosexuality or otherwise, and may want to terminate their employment because their state labor board allows them to do so?In some states there is no sexual orientation protection, hence LGBT+ are not protected... but so aren’t straight individuals.
See here https://www.americanthinker.com/articles/2014/11/the_29_states_where_you_can_be_fired_for_being_straight.html
You can stretch reality all you want, but the truth is what I suggested happens far more than your innocent suggestion. In some states, there exists no statutes that protect minorities from hate crimes outside of race and religion. What then? It's a common occurrence to see a straight couple glassed in the face as much as two blokes or two lasses?