Think of it this way;
If it's in your car, you WILL be held at least partly responsible when you get pulled over and the cop finds it.
I know this because I've seen it lol.
Also, people on "hardcore" drugs are unpredictable. Can be simply annoying one minuet, violent the next. Not because they mean you harm, but sometimes it just happens. We all know drugs alter our brain chemistry, cause us to act out of character and do things we wouldn't normally do. Giving this person the boot probably was the best decision you made all day lol.