Well no, it is still bestiality, but we only associate bestiality as taboo because the animal lacks the ability to consent. Khajiit and Argonians have sentience and can agree to any Union, thus it loses the reason why it's taboo. There should definitely be options to Mary Kajite, but it's an easy fix. Just assign the NPC of your choice to the right faction and ask them to marry you.
Incorrect for multiple reasons. It is not taboo due to lack of consent but for sociological reasons, as it is legal in some countries (not that I agree with it, but it helps prove the point). Second, while Khajiit and Argonians resemble animals, they are not the biological equivalent. By this logic, it would be bestiality to bump uglies with a human because they're anthropomorphized apes. Since Khajiit and Argonians are "humanoid" in shape and mindset, they are humanoid by definition. Finally, using the console isn't a viable fix for those who only have console copies and those that do have it on PC have to deal with the lack of marriage dialogue.