Not true. Alcohol lowers inhibitions, impacts rational thought and increases aggression. Even if you were to say that alcohol only takes away inhibitions, those inhibitions are still part of someone's character.
The "a drunk tongue speaks a sober mind" is basically nonsense. I'm not sure why some people have this obsessions with saying that someone under the influence of a drug that literally alters how a person thinks and acts is suddenly the real them. I guess they just want to be able to point the finger at others.
It's rather like saying that when people get drunk, they fall down, so this is showing that people really want to fall down all the time, that falling down is the real them, but they manage to keep the falling down in check when they are sober. Then, when they get drunk, the real them comes out and they start falling down.
https://www.drinkaware.co.uk/news/how-alcohol-impacts-our-behaviour