C-SPAN is totally 100% controlled.

Either the callers are all actors, pre-screened, or steered subtly by the hosts.

They always make it appear like the opinions of Americans are 50/50 split regardless of how many call in from one side.

However, it does seem like they're setting democrat and anti-Trump republicans for failure. They gave the last word today to the most sane viewpoint on the "trial" thus far.