There are lots of Green voters who would vote Trump, I think.No, they ain't that stupid to vote for someone who pulled them out of the Paris Accord, and called Climate Change a "Hoax"!!
Remember, some are just voting Green because they think Democrats suck but would feel bad about themselves if they voted for Trump or the GOP.
Without the Green option there, they might just hold their nose and vote for Trump.
As always, voters of any party in a FPTP system can't be assumed to be a monolith all voting for that party for the same reasons.
You get very little information about a voter's real preferences from that kind of ballot.
It's one of the many things that a systemic reform would help with, because the ballots under lots of other systems are more expressive.