I didn't read the full text of the original study, but someone pointed out that "social-behavior factors" didn't include the amount of time spent hanging out with friends/colleagues/family and drinking.

The reason I take this study as any evidence at all is that it's not the first such study to indicate that drinking increases lifespan, and because they did control for quite a few things.

The link didn't work for me but assuming it refers to this study, controlling for socio-behavioural factors (which includes measures of social support) significantly reduces but does not eliminate the effect.

[We study] the association between alcohol consumption and all-cause mortality over 20 years among 1,824 older adults…. Controlling only for age and gender, compared to moderate drinkers, abstainers had a more than 2 times increased mortality risk, heavy drinkers had 70% increased risk, and light drinkers had 23% increased risk. A model controlling for former problem drinking status, existing health problems, and key sociodemographic and social-behavioral factors, as well as for age and gender, substantially reduced the mortality effect for abstainers compared to moderate drinkers. However, even after adjusting for all covariates, abstainers and heavy drinkers continued to show increased mortality risks of 51 and 45%, respectively, compared to moderate drinkers.