Heres an idea.

Take a bunch of pictures of your work and put them.
In as many local sporting goods stores you can.
With letters from your past custmers and what they think of your work.
If they were satisfied or not.

And let them make up there minds.

And check with a lawyer to find out what,
Legal options you have about this guy.
What he is doing is slander and is ilegal.

I hope this helps

Good Luck