If it is true that natural law is found in the hearts of men, then it is based on society’s concept of morality, which in turn is a function of time. As such, should everyone not, in our hearts, have empathy for gay people? After all, gay people are human beings too.
Putting on asbestos underwear now, lol...
If morality consisted merely of societal values that are self-created and temporary, "a function of time", as you put it, then it would be relative. As such, moral laws would not be universal and unchanging but would be reduced to relativistic preferences rather than prescriptive requirements. In that case, it would make no sense to use the word, "should" (a prescriptive) as you do with regard to having "empathy for gay people".
The assumption that that the natural law is based on society’s concept of morality, which is a function of time, is self-defeating.
Cordially,