In my view, the personal political leanings of J&D in 1965-66 are of little consequence.
Both sides were fair game. I mean, we're talking about Jan & Dean here. "Universal Coward" poked fun at the anti-war movement -- and "Eve of Destruction" was -- to quote a phrase I've used before -- delivered with "exaggerated angst." And the latter was on Folk 'N Roll because it had just been a #1 record for Barry McGuire (and the tie with Sloan sealed it).
The problems between J&D by that time went far deeper than Dean refusing to be part of "Universal Coward" (or any other song Jan was working on at the time). And if Dean was standing on political principal in that case, he certainly turned right around and sang on "Only A Boy" in early '66. And Dean is definitely singing on that record. You can clearly hear him, but the session tapes remove all doubt. So that kind of wipes out the political argument, in terms of Dean's refusal to participate.
According to Roger Christian -- who was as close to Jan as anyone -- the establishment viewed "Only A Boy" as an anti-war song -- because it was soliciting sympathy for a kid (a soldier) who's life had been snuffed out before it really began. And Roger said the DJs at his station were told not to play the record. Strange, given the popularity of the Sadler tune. But despite the Youth Movement, the country was still divided.
So again, whether Jan was personally Right Wing, Left Wing, or somewhere In Between, is -- in my opinion -- immaterial.
By the way, the flip of "Universal Coward" was "I Can Wait To Love You" on Jan's solo single. And when Dean sold his Rainy Day masters to Sundazed for their '96 release, he took the backing track for "I Can't Wait To Love You" -- a Screen Gems master written and arranged by Jan -- and sold it to Sundazed as "Rain Clouds Long Gone" (replacing the song's true writers with his own songwriting alias -- Nat Ormsby).
Remember, too, that Dean is currently a Republican residing in Organe County, a Right Wing enclave in Blue State California.
I think you'd have a hard time trying to paint Dean as a Liberal.