1You are right that the first drink takes the edge off. That is exactly what makes it hard, and pretending otherwise would only be untrue.
The calm is real at a small amount and it turns on you as the amount climbs, which is why the argument at eleven at night bears no resemblance to the ease at eight. Most people have worked this out from their own evenings without ever putting it into words. Saying it plainly usually helps more than being told that drink does nothing for you, since you already know that it does something.
Islamic evidence
There is great sin in both, and some benefit for people: the sin is greater than the benefit (Quran 2:219). The benefit is not denied, it is weighed, which is a more honest conversation than insisting there was never anything in it.
“They ask you [Prophet] about intoxicants and gambling: say, ‘There is great sin in both, and some benefit for people: the sin is greater than the benefit.’ They ask you what they should give: say, ‘Give what you can spare.’ In this way, God makes His messages…”
Qur'an 2:219
Psychological evidence
In an experiment where alcohol was given to both partners before a naturalistic conflict discussion, being intoxicated changed the balance of positive and negative behaviour in the conversation. Drinking does not leave a disagreement where it found it. It was a laboratory set up with a set task, so it tells you about the direction of the effect rather than about what happens in your own kitchen.
Testa M, Crane CA, Quigley BM, Levitt A, Leonard KE. (2014). Journal of studies on alcohol and drugs · doi
Review detail
Why it works. The same drink can settle you and then, a little later, take away the restraint that was keeping you civil.