They mentioned he wasn't much of a scientist. Their goal is also to focus more time on lesser known characters in the history of science instead of being just another show talking about Galileo and Da Vinci. Also Macfarlane essentially paid for it, and used his pull with Fox to get the show made, he wasn't writing for it. Brannon Braga from Star Trek is the director, Carl Sagan's Widow, a couple other former writers of the original Cosmos, and Neil deGrasse Tyson worked on it. It's also absolutely delightful.
I just watched the first episode and I enjoyed it. It's a tough line to tow to create a show of this magnitude that can be accessible to scientists, non scientists and young adults all while paying homage to Sagan's legacy. If anyone has issues with McFarlan or Tyson, my suggestion is to set them aside and judge this on its merits. So far, so good IMO.
Tyson calling Seth a genius And saying that family Guy has a lot of science in it on Science Friday marked him as a rube.