Pure alcohol has a BG lowering effect.
The problem is that many drinks containing alcohol also contain a lot of sugar and carbs.
Beer is bad in that respect, as is sweet white wine, liqueurs, sweet sherry, port and so on.
Dry white or red wine is OK as are most spirits, dry cider is good and so is dry champagne (or Cava).
The biggest danger is that consuming alcohol makes you hungry, it also clouds your judgement, so you finish up eating fish and chips or a curry on the way home!
H