Depends what you mean by "bad." If by bad you mean the guy in your description, then, in that case, I'd say yes, avoid him. If you mean you, as a leader, have to practice with beginners or those less skilled than yourself, then Id' say, no, you can make that work but it'll take time and you'll be doing the teaching and will always be somewhat ahead of your partner.
This is it in a nutshell. I have been that innocently bad beginner learner, wishing like crazy for a more advanced dancer to practice with me. I know now that what I really wanted was Free Teaching but I called it "practicing." Completely understandable, but also somewhat unreasonable. But I didn't know that back then.
Back in the day, I contacted a couple of people through a dance-partner-search website, and "tried out" with one of them. He was considerably more knowledgeable and skilled than I. At the end of the tryout, he basically said, come back when you've learned something.
Was he wrong? Not really. He didn't want to be my Free Teacher. I know now that's fair enough, and that I could have hurt him and basically impeded his own dancing.
A few years later, I had learned a bit, and Guy 2 asked me to practice with him. Now, I'm not saying I was skilled and experienced, but I was a tiny tiny bit more knowledgeable than before, and more aware of what's what than Guy 2 -- to such an extent that I realized that what he really wanted from me was Free Teaching but he called it "practicing." He wanted someone to help him learn. I politely declined, partly because I was pretty sure that I didn't really know squat, and 100% certain (from experience) that he would hurt me.
Was I wrong? I don't think so. I continue to dance with him in group classes and at socials. As the years move along, he has remained the same dancer while I have studied and learned and, I hope, improved.
Guy 3 has asked me both to be his practice partner and his lesson partner. I have politely declined. He has now found a lesson partner and is taking lessons at a different studio. Of course, he will ask me
at a social if I can help him work through what he's been doing with his teacher and lesson partner. I fall for it almost every time, because I dance with him at socials and it's more comfortable to do that when he's not pushing my shoulders behind me, or off--time, or... But I will not be his lesson partner or practice partner, because he's motivated by money and is actually pretty up front about it*. He wants Free Teaching, but calls it "practicing." And he will hurt me, as I know from experience.
Am I wrong?
*"I spent $500 on Viennese Waltz, I should have it right by now," verbatim quote