My answer would be that sexuality involves a 'telos', which is to say, an end for which it exists. While in some circumstances homosexuality may not harm the persons involved, it definitely changes what sex is 'for'.
We must interpret the reason for the command being that at the very least, what sexual intercourse or in general, the sexualization of a relationship, is for, is affected for the negative by the normalization of homosexuality. For one, the term 'sex' becomes somewhat odd, since 'sex' refers to complementary parts of a whole.
Also, it should be noted that having strong affections for or attractions to a member of the same sex is not the sin, but the act of 'doing what you'd do with a woman, with a man.' We can only infer that in a society where a woman has 'sexual choice' like men did in those situations, female homosexual acts would be likewise considered wrong.
What makes this a hot-button issue is that usually what people reject or object to is not so much the acts but the mere attraction, which is often something a person cannot help.
Additionally, the normalization of homosexuality makes it very hard for men who have strong affections for one another to keep their relationship asexual. Again, if we accept homosexual acts as normal then the 'reason' for their relationship may be interpreted differently.
This comes at it with the idea that attraction or strong affection is not necessarily sexual, but is sexualized in the context of a marriage, which in this context means male and female.