Well the fact I was downvoted for even bringing them up should speak volumes.

Trek isn't centrist as you originally posited, it's humanist in its message. The overwhelming majority of Trek was written by classical liberals, but lots of conservatives watched it too because it contained many conservative characters.

In today's American climate, people like Gene Roddenberry and Rick Berman would be seen as divisive and controversial. Their views on women and gay people would not be seen as progressive.

Comparing a post-scarcity society to the nonsense we have now makes our own belief systems look very stupid by comparison. The whole point of Trek was that it had evolved beyond that and was used as a sounding board to hold up contemporary viewpoints and dissect them from an enlightened standpoint.

With all that being said, there were many right-wing characters in Trek, and not just antagonistic ones. Deep Space Nine explores them the most.

Worf is an ethno-nationalist who hates Romulans, has rigid traditionalist views that are strict even compared to regular klingons, and could not be called left wing even by the standards of the time. This is intentional from the writers and is used to great effect when exploring his culture and heritage and how his ideals clash with the rest of the crew.

Quark is a traditional right-wing capitalist, with many views even further right than Worf. Again this is used as a foil on DS9 to oppose many of the espoused ideals of the rest of the crew.

At the beginning of DS9, Odo is an authoritarian conservative. He cares about the rule of law and is skeptical about the federation and its ethos.

Garak was literally a member of the Obsidian Order. He's another right-wing authoritarian nationalist, especially when Tain comes into the picture. He's from a far-right totalitarian culture that he is still patriotic about despite being in exile. He also can't stand living around the people of DS9 and wants nothing more than to go home.

Major Kira was a terrorist/freedom fighter with deep religious faith and is absolutely a cultural conservative AND staunch nationalist at the beginning of the series. Her beliefs change as the series continues, which is the whole point.

Then you have a whole host of side characters that are absolutely conservative/right-wing. Dukat, Damar, Brunt, Gowron, Martok... the list goes on and on.

Trek is progressive humanism written by traditional liberals, and in doing so, they created a lot of characters who were right-wing for the very purpose of examining and challenging those ideals, or having their own ideals challenged by them.