This is the sciencey bit.....
Alcohol is a powerful inhibitor of gluconeogenesis. In fact, it forces part of the gluconeogenic metabolic process into reverse. This means that if all the glucose in the blood is being derived from gluconeogenesis then the consumption of alcohol will inevitably cause the blood glucose level to fall. Worse still, the alcohol also stops ketone body production, thus leaving the brain entirely without fuel.
A person who is ketotic is 100% reliant on gluconeogenesis to maintain adequate levels of glucose in the blood. If, under these circumstances alcohol is taken, the person will become disorientated and might lose consciousness, not just from the alcohol, but from low blood sugar. Needless to say, this could be very dangerous, and even fatal.
Alcohol does not have these effects if the glycogen stores in the liver are normal. Under these circumstances the blood glucose level in the blood is maintained by the breakdown of liver glycogen, a process that is not influenced by alcohol. If a person becomes confused under these circumstances it is due simply to the pharmacological effects of the alcohol!
Basically alcohol halts the ketosis process, so if the only way we are getting fuel for our body is through ketosis (which if you are in ketosis, is almost certainly the case). Then drinking MAY cause your body to be starved of fuel (that includes your brain, kidneys, liver etc).
I am sure there are plenty of people who have drunk alcohol while in ketosis and I'm sure there are many that have been fine. However, that doesn't change the science behind it and it's better to be informed before you make your own descision on what to do.
There are plenty of people who use recreational drugs on a regular basis even though we all know it's bad for you.
If you are going to drink while in ketosis, at least make sure you let the people you are with know that is you get sick, to let the docs/ambulance etc know what diet you are on.