If the only differentiator and "secret sauce" in your product is a bunch of CSS and some D3 layouts, you've got a problem.

Stop whining and start creating some real backend system and process so that you can offer real value to your customers. I bet you would love to get patents on those charts and color combinations uh?

You're creating a straw man. I don't disagree that he's copied you. I disagree that it's stealing. I don't think what he did is wrong.