It doesn't matter if poison A is more dangerous than poison B in the short term. They're both poisons in the end. And tolerance to poison doesn't exist.
Being able to "drink more alcohol" before you get the total retardation effect or even the mild retardation effect doesn't mean you're "more tolerant". It just means your body needs to reach a certain level of compound, internal damage before the effects manifest, and it may be faster to heal certain afflictions at certain does, or have stronger process for building and keeping the myelin sheet around your nerves and tracts.
Your liver also never heals from wounds that are inflicted by being overworked by anything, including alcohol. The liver only scars, and beyond a certain level of scarring, you get liver failure, which is a serious thing.
I don't understand something: why would someone want to drink themselves into a stupor, or even in more "moderate" quantities drink something that clouds their mind and numb their senses. Does that really make sense to you?
Just because something is allowed by Clergy or anyone, it doesn't mean that something is quintessentially a net positive for you, does it? Veganism is allowed by our food ethics. Is veganism a healthy diet? No, and you will see / understand as you spiritually that you cannot be a vegan nor a vegetarian. Not because somebody tells you so, but you reach an understanding of your body that simply doesn't it make it legitimate nor excusable. Same with undereating, overeating, eating unhealthy foods of any kind, being fat, being overly muscular, being too thin.
Embodying virtues like Harmony, Balance, and Temperance is part of spiritual advancement. Wisdom, Truth, Justice, Beauty... all virtues that tie into this as well, as do others, as all 36 core virtues are inter-related.
Going back to the original question, yes, alcohol damages your soul in any amount. How much is the damage and how fast you heal depends on many factors. I have replies and post where I discuss some of the physical damages of alcohol. Read them. Make the connections between the physical damage, and the area of the soul it's related to or ruled by (i.e. Leydig cells in your testicles are ruled your your root chakra).
Also, what classifies as "heavy drinking" changes from culture to culture. Some culture, like the British one, have embedded heavy drinking, so their idea of light drinking would look excessive to more relaxed cultures (i.e. Southern European ones). A British rugby lad drink 10+ pints of average beer or cider in a night out without batting an eye, and that's considered normal and is also considered heavy by British standards outside of rugby circles and university sports. This is to make an example, and show you how British people get international reputations for their "rowdiness", which they consider normal social behaviour when it's not considered normal in most of the world. So norms can change by country.
Lastly, as somebody in this topic already said, you don't go from heavy to "puritanism" overnight, unless you genuinely don't give a shit about this and thus you're not really addicted. If you're addicted, you taper down gradually up to a point that is not pathological and that is comfortable with your current level of advancement. That's the idea.
And, yes, you can be heavy drinker or have strong compulsive behaviours without being addicted to them. Being heavily into something harmful isn't the same as being addicted to it.
Addicted? -> gradual taper to a non-pathological, comfortable level
Not addicted? -> easy, immediate taper to a non-pathological, comfortable level
Another thing I will say: moderation, as far as my understanding goes, does not apply to poison. This doesn't contradict what I said when taken as a whole, because you can keep engaging in a behaviour while striving to advance and reach a point when you're not dependent of it. With poison you get 0 as the moderation, and excess from any non-zero volumes. Beyond a certain amount, it's a pathological excess that varies by substance. Some poisons kill you instantly, obviously, rather than have mild responses like the fever, nausea, headache, and other common poison-fighting behaviours of the body. With poison, there is no such thing as deficiency.