I've been with my girlfriend for 3 years now and she's recently gotten back into contact with a couple of old friends. She's been out for drinks with them a few times since they've been back in contact.

One of the friends is seeing a guy who is quite a big drug user from when her friend has said and just doesn't sound like a good guy to be around. Her friend suggested to my gf that the four of us go on a double date.

My girlfriend mentioned this to me after getting back from seeing her friend but I refused. I said her friends boyfriend doesn't sound like someone I want to be around at all.

I've had problems with addiction in my family and hate people who abuse drugs casually and act like it's nothing. My girlfriend said it would only be for an evening but I still refused.

I've been on other double dates with my gf and her friends. She said I should be alright spending an evening with them but I just repeated that I didn't want to. How would you handle this?

Tl;dr my girlfriend wants us to go on a double date with one of her friends and her boyfriend but I refused as her friends boyfriend is a drug user and just an unpleasant person. My girlfriend said I should be fine with going as it's only one evening