By attending the SOTU, to laypeople it makes it look like scientists agree with the president's positions on climate change.
Unfortunately, I believe this demonization of Bill Nye is appropriate.
Edit: I believe if you want to change behavior, you model the behavior yourself. If you shut yourself out of the discussion, then so will others. You don't tell people how to fish, you show them how to fish. You don't tell people to learn science, you show them the science.
Bill Nye circumvents that community completely but yet still represents an entry point of science for many(most?) laypeople.
I don't think laypeople are nuanced enough to know that a "science guy" isn't a "scientist". So it's setting back scientists a little bit from a PR perspective by having this hack be seen publicly associating with the Trump administration.