Alcohol is safe to drink in moderation and can actually benefit your health and help prevent kidney stones, kidney disease etc.
However when alcohol is consumed in excess then yes the alcohol can become a poison.
You can actually get alcohol poisoning which can kill you if not treated in a quick enough manner.
I've had a few friends that died of alcohol poisoning as they would drink a lot of beer, whiskey etc.
The alcohol poisons the blood because the body cannot get rid of the alcohol fast enough.
Then the alcohol leads to alcohol poisoning and then eventually death.