If the sophist is doing it dishonestly, then I would say yes, it is dishonest. But I also believe that people can argue and discuss, even teach, in a sophistic way, and do incredible good.

Check out Wikipedia:

"Sophism can mean two very different things: In the modern definition (from Plato), a sophism is a specious argument used for deceiving someone. In Ancient Greece, the sophists were a category of teachers who specialized in using the tools of philosophy and rhetoric for the purpose of teaching aretê — excellence, or virtue — predominately to young statesmen and nobility."

and later...

"The practice of charging money for education, and providing wisdom only to those who can pay, led to the condemnations made by Plato in regard to their profession itself being 'specious' or 'deceptive', hence the modern usage of the term."

So it definitely has a negative connotation by modern day standards, but if you think about it, there are many people who teach and profess 'excellence' for money. Do they all deserve the negative aspect of the label of sophist? I've had really great teachers that used 'philosophy and rhetoric' (and perhaps a few other means) to teach me, or to spark good discussion. Just as I've had a few teachers that were clearly only teaching to keep getting paid.

What your question makes me wonder, though, is:

Can a teacher, or a sophist, intentionally deceive you to teach you something? What about anger you? Or even hurt you to help you grow, change, and learn?

Perhaps I'm thinking more along of the lines of apprentice, but I think it's an interesting question nonetheless.