Trump mocked over his new design for Space Force uniforms: ‘The evil bad guys from Star Wars’
(www.independent.co.uk)
There is a wide realm of literary subtext between "obvious satire" and "full-throated support".
I don't want to be rude, but it really seems like you heard someone on the internet say Starship Troopers was fascist and Heinlein was pro-fascist for writing it, without really evaluating either of those claims for yourself.
The concepts explored were not fascism. The main political concept explored was tying voting rights to civil service, and the vast majority of that service was non-military. What about the book made you think it was exploring fascism?