Gadol, MB suggests that sweet wine is exempt from drinking in two gulps. Given popularity of bad sweet wines in US, maybe this is a heter used. So, lifnei ever – you give sweet wine to people without manners.
Historically, NY Jews were drinking NY wine and only sweet stuff grows in upstate NY. Then, RebE and the rest of the kahal acquired taste for this sxweet stuff.
St some point NY wine was monopolized by Manischewitz sweet and was subject to Rabbinical boycotts – that wa the appropriate time to use chalah in the evening and mashke in the morning.