We have all witness intoxicated passengers on flights but typically, they walk on the plane already sauced vs. an event during flight pre-boarding. I won't speculate but is it possible your conversation of church & politics touched on sensitive or overly politically correct nerves which results in someone opposing your viewpoints feel they take responsibility of reporting you inaccurately intoxicated? E.g. If you reported you were certain religion or ethnicity I could say that was it (not claiming race card but the unique token in a room is sometimes observed more closely), but seems very strange 3 beers unless you guzzled within 30 minutes instead of 2 hrs would've caused such an outcome.
Unless, you are a naturally loud talker, was already drunk/hungover before your first flight, hard of hearing or had on headphones during part of your conversations this seems a bit intrusive.