Forget scripture tag...it won't work. JWs twist scriptures to fit their dogma as they please.
You're at a point where you're just going to have to say that you don't accept all the JW teachings and you're not interested in investigating it any further.
Oh, they'll probably act hurt that you don't want to be part of what they've embraced. They'll put the guilt trip on you. But remember, they chose to go down this path, not you. You're willing to be friends despite the difference in religios belief. If they can't accept you as you are, as you have always been, it's their loss.
Nothing you did, or are doing, justifies them to break off a friendship...but it's entirely possible that they will. Even if they accept your decicsion to not go any further with them on the JW thing, you'll notice over time that they'll see less and less of you.
It's tough...we know. Many of us have lost friends. Many have lost even more. Parents, siblings, even children have put this religion over their relationships with their own flesh and blood.
Good luck and hang tough