Relax. I am 40+ years old. When I visit my parents they object to my “revealing, not modest and not appropriate” clothing. I am married with 4 kids. Parents are … parents, forever. My parents still have a 10 pm curfew for me 
I visit them once per year, and I think they still consider me to be 16 years old.
Of course you should not be drinking in your parents home, particularly hosting a party of some sort!
That said, if your parents continue to criticize the whole concept of adults drinking alcohol responsibly, I’d be tempted to ask them how it can be a sin, since Jesus was known to drink wine, and even turned water into wine at a wedding!
If they’re anything like some fundamentalist evangelical sects like the more extreme members of an evangelical church some exceedingly religious fundie relatives attend, their mindsets would be such that they’d be impervious to such logic and reasoning…however sound and reasonable it is to most of us.
While those older relatives were not so extreme to criticize and try imposing their way on weddings and other extended family social events on less religious older relatives who were hosting, they did have a tendency to give annoying obnoxious lectures about “excess drinking” to folks in my generation(the young’uns). Even those of us who are in our 50’s and only had one glass of red/white wine for the entire event.
Most of us have long learned to just ignore them with some encouragement/abetting from other older relatives who reject that mentality. It also helps most of their own kids feel they are being ridiculous on this score.
If my parents tried to tell me it’s a sin to drink alcohol, I would respond that I disagree, I will do what I want when I want. Of course, I would abstain in their home, but I wouldn’t tolerate lectures on the evils of moderate drinking, particularly if it is given with respect to morals rather than health. YMMV.