Well, it depends. For example, unless the dentist is doing research, I won't consider him a scientist, and I definitely wouldn't ask him questions about evolutionary biology. I would ask an evolutionary biologist that. One thing to realize is that biology is a huge field that encompasses many areas and having a Ph.D. in some area in biology doesn't mean that they know all of biology.
However, the most important thing to realize, and I'm sure other TEists feel the same way, not having a degree doesn't mean that the person's views are invalid. It just means we have to look extra carefully at their claim. Likewise, having a degree doesn't mean that a person's views is automatically correct, we still have to look at their claims.
Case and point, Behe has a Ph.D. in biochemistry. I'm sure he knows biochemistry very well. In fact, if you look, he has many papers published in biochemical journals. However, this doesn't make his views on intelligent design correct. He has no papers published in intelligent design. What it all boils down to is evidence, and that's what all the Creationists forget when they trot out all these Ph.D.'s.
EDIT: Also, we don't say that people with no degree in biology doesn't understand evolution, we take what people say in order to prove it. For example,
Martin says that the academic world knows the big and difficult questions the likes of the Bombardier Beetle ask of evolution, but conveniently ignores them. In the rarefied scientific circles most lay people don't follow or understand, he says, more and more people are admitting that, like an attractive jar with a hole in the bottom, Darwin's theory just doesn't hold water.
However, if you google scholar, you'll find hundreds of papers that discuss the evolution of the Bombardier Beetle, hardly ignoring it. On top of that, evolution doesn't produce entire systems at once, nor does it produce a bunch of useless systems until the last one is in place that makes all the other ones successful. These things that Martin doesn't know/discuss shows his lack of knowledge about evolution.