Avoiding Working with a Potentially Arrogant Researcher
Dismissal of previous research in the field is not problematic in itself. As you concede in the question, you may even share this assessment. The possible problem, which you can't really assess from one general comment like this, is whether the researcher lets that opinion drive his research in inappropriate ways. I'd say that's a question of emotional maturity. Does this person need to be right where everybody else is wrong, in order to feel fulfilled or successful? That would be a big problem. But, being overly risk-averse, and "going with the flow" too much, could also be a problem. In science, the main thing is to look at evidence dispassionately, and draw conclusions based on the scientific method. Any character trait or emotional immaturity can threaten one's ability to do that.

TL;DR: It's not a problem in itself, but it could lead you toward some worthwhile inquiry. Focus on the person's ability to manage their strong opinions or emotional dispositions and integrate them into appropriate scientific techniques, not so much on the specifics of what those opinions or emotional dispositions are.