The Bible verse you quoted is in context of the church; there are those sowing false doctrine. They are to be avoided. Actually, they are to be kicked out.
I think it is an incorrect stretch to interpret it to mean that we can’t have any relationships with liberals.
I do think you are free to disassociate with liberals if you want to, of course. Sometimes that wins people over, when they see how strongly you feel.
Other times it is best to continue the dialogue. Not everyone at FR has been a conservative all their lives. Many of us were persuaded to become so in one way or another.
We are almost at the point the Israelis are with Iran. Iran wants to eliminate Israel. So, how does Israel begin to strike a civil coexists with Iran?
After Billy boy was elected, politically ignorant me got into a conversation with a co-worker who listened to Rush Limbaugh at work. Our conversation was over health care funny enough. The co-worker was a jerk in some ways, but he was right in his politics. He questioned me about what has the government ever run that has worked out well. It left me speechless. I was a non thinker at the time. A few years later (1998), I’m listening to Rush Limbaugh and so began my conversion. So I can’t credit the co-worker with my conversion—it really was a combo of a few things in my life, but I often think back to my conversation with him. I’m probably further to the right than him now!
Any "dialog" with a liberal is a total waste of time. You might as well go discuss politics at the local sanitarium.