What about simply ignoring the communications that come from this
guy? In fact, you can even remove the connection on LinkedIn after a
short while if you want to, and the other person doesn't see it
happen directly. I've done this, and also removed endorsements I
made over a year prior, after which I decided I didn't have the same
level of confidence in the person. My personal philosophy is that I
don't want any toxic connections in my LinkedIn network, and no one
that I don't have confidence in as they are a reflection of me,
however remotely.

Kristina