I was on low carb diet for many years before I ventured into CD - (which btw works much better for me than LC)
I often had a glass of red wine whilst in ketosis, and never noticed any side effects, or issues. The liver breaks alcohol down into ketones so there's no reason to suspect it takes you out of ketosis. It can make you tipsy a bit quicker due to the way that alcohol breaks down. Your body will always use alcohol for fuel if available, so you may slow your weight loss. But as for it being dangerous - I do not understand why from a chemical perspective. I see glycogenesis mentioned, but as the brain can run on ketones instead of glycogen, it's not an issue.