I think the problem is that when we are part of the majority (I'm assuming you are chinese middle class singaporean?), it's easy not to empathise with minorities
I think comparing 377A to theft is comparing apples to kaya toast.
is your issue with homosexuals displaying affection in public?how is that different from me and my girlfriend making out in public.
Homosexuals are going to display affection in public,same as heterosexual couples. 377A is not going to stop them.
If you are afraid of the differences that homosexuals display compared to conservative asians (you mentioned openly displaying affection, sounds very european actually...), then the issue is not to try to force them down with the law, but with discussion to come to a point of understanding where social and cultural norms are in Singapore.
If homosexuals were exactly the same in terms of outward appearance, dressing, etiquette, etc, except for the fact that they had sex with others of the same sex, would you raise an issue?
I don't think that we are in the position to judge what God deems as right or wrong (apart from the 12 commandments perhaps where it's literally "set in stone")
Neither can we decide whether procreation is the ultimate role of the human race
I think each of us can make our own decisions on what we consider normal (I don't find indians sticking rods into themselves during thaipusam normal...), but it is a dangerous position when we start enforcing our beliefs on others (which is exactly a recipe for all sorts of strife, including racial and religious strife)