One quote, from one guy, who was asking a question not positing an answer. That's a pretty shakey assertion. I don't see beverage consumption as an absolute zero sum game, and I don't see any real evidence that alcohol intake had markedly decreased in the time period charby referred to.
Well, as we don't have surveys and statistics from the time period, there will be very little but reasoning and extrapolation to come to a conclusion.
I will, however, argue that beverage consumption can be a zero-sum game. If you have tea instead of beer with a meal, are you going to try to make up for the lost alcohol later? I realize people could have a beer and tea with their meal. I don't have any data that that did not occur. However, there is an absolute limit to the volume of liquid an individual can hold and, having drunk a good amount of tea myself, I find it rather uncomfortable to drink significant amounts of tea AND significant amounts of other beverages.
I think, also, the stats of:
Between 1720 and 1750 the imports of tea to Britain through the British East India Company more than quadrupled
and
By 1766, exports from Canton stood at 6 million pounds on British boats, compared with 4.5 on Dutch ships, 2.4 on Swedish, 2.1 on French.[9] Veritable "tea fleets" grew up.
suggest that tea drinking had been adopted almost universally.
If my contention that increasing one type of drink will crowd out some other previously drunk beverage, that makes a good case for tea decreasing the general state of drunkenness.