Let's first look at the fact that I am not a scientist. The definition of scientist is as follows:
"A person engaging in a systematic activity to acquire knowledge that describes and predicts the natural world. In a more restricted sense, a scientist may refer to an individual who uses the scientific method."
Now let's look at the definition of expert:
"A person who is very knowledgeable about or skillful in a particular area."
A scientist is a person who acquires knowledge and an expert is a person who learns about and understands the information acquired by the scientist. We aren't all scientists. It takes scientists to figure out how to design a working helicopter, but it takes an expert engineer to build one and an expert aviator to fly one. Most helicopter pilots would be unable to build one and most helicopter engineers would be unable to fly one. Then there are scientists who not only figure out how to build better helicopters, but can also engineer and fly them. Having said this, you don't necessarily have to even be an expert to fly one. Every pilot has to start somewhere, right?
For over 150 years, scientists have been studying and acquiring knowledge that contributes to the continually developing theory of evolution. These scientists have provided the information and all we need to do is learn this information. A person who studies a particular topic, such as the theory of evolution, is usually an expert compared to those who don't understand it at all. If you are unsure about someone's expertise on a particular topic, just check their claims by going back to the original source of information provided by the scientists.
Let's look at the second claim made about me. I have to take a scientist's word on faith. The two definitions of faith are as follows:
1. "Complete trust or confidence in someone or something."
2. "Strong belief in the doctrines of a religion, based on spiritual conviction rather than proof."
Usually, when someone accuses you of accepting a scientist's word on faith (yes, this is an accusation), they are using a logical fallacy called false equivocation. This means they are using one definition of a word that doesn't match the context in which that word is being used. In this case, the accuser is using the second definition of the word faith which is belief without evidence rather than the correct definition which is trust or confidence in the scientist.
Now even using the correct definition can cause reason to doubt considering the fact that it's possible to trust someone who is wrong, but trusting a scientist's word doesn't by necessity have to be by belief without evidence. Trusting a scientist can and should be based on looking at the evidence presented.
Bill Nye is often ridiculed by doubters for not being a scientist. As I've demonstrated, there's a difference between being scientist and being an expert. You don't need a PhD in physics to pilot a helicopter. You don't need a PhD in biology, paleontology, geology, zoology, chemistry, molecular biology, taxonomy, mathematics, cosmology, physics, probability, anthropology, archaeology, history or philosophy to learn about and be an expert among your peers on how evolution works.