I’d leave the biker enough room to shoot / slide through, no way could I take him (or her) out with my two tons of metal. That might mean I collide with the car coming towards me, but I’m hoping the driver will see their error and get back into their own lane. If I die then at least I don’t have to live with crippling an innocent biker.
I’ve been a biker in several countries so I’m always looking out for them if I’m in a cage. I’ll pull near the curb to let them through and almost always get a cheery wave as they blast past. Gives me a warm, fuzzy feeling inside. 