Homosexuality, smoking, drugs, and Down's syndrome

(stuff I typed on a Whatsapp chat)

once I made my GP class think about it
'why do some people regard homosexuality as wrong?'
'religion, culture'
'But you see even the non-religious and non-traditional criticising it. Why?'
'...it just looks weird, not common'
'yeah, it looks unusual and weird. And when you have religion and tradition to back you up against this weird thing, society can consider it legitly wrong. Now think about a Down's Syndrome adult. Doesn't he look unusual and funny too? But you would never ever dare say it's right to shun him, because you can't back up your subjective claim with any argument given by any other institution or respectable person, and people know that Down's Syndrome can't be helped, and what society expects of you is to accept them and treat them with care.' I could even see some of the students looking a bit shocked that I was saying this, putting Down's Syndrome and homosexuality in the same breath, but that's my point exactly. Getting them to think about why they think what I'm saying is shocking or why their own perceptions are as such.
My point is that when someone finds a minority's behaviours weird and they have powerful institutional backing, they become extremely imposing and assume they're right without really questioning why they think this way. Even if they're not religious or anything.
I used to want to tell the people who gossiped, 'why is it wrong? If you're looking to the Bible to support your point, isn't slander a sin too?'
Basically ya. Gotta challenge what you see as abominable
Hey, some drugs were legal once. Smoking and drugs are amoral, not immoral. The only reason they might be considered sins is because they're unhealthy.
And because you'd be a bad witness for Christ by doing it. Why? Because of how society sees it. Not because it's immoral.
But along the lines of unhealthy, that makes me equally sinful by sleeping so little and eating so much Old Chang Kee for lunch and never exercising. I don't deny it. I'm not taking care of my body, this vessel of God's.
But why are the other things I mentioned viewed as so much worse?