I wouldn’t say that it was darker, so much as that it just sucked.
Support Your Local Sheriff might have been the anomaly. The same director gave us Dirty Dingus Magee and Mail Order Bride. Both are nearly unwatchable comedy westerns. In addition to that, he is responsible for two Wild Wild West TV movies that are notable only for being a little bit better than the Will Smith travesty, despite having Robert Conrad and Ross Martin. In fact, a look over Burt Kennedy’s IMDB page shows he directed a lot of shit movies.
I loved this! All the “veterans” were so impressed with themselves and their ability to survive in their “big country”, and convinced that newbie Gregory Peck was a helpless kitten doomed to death if he wasn’t watched like a kid. And to him, a guy who sailed the featureless oceans, their big country was hardly more than a pond.
This is a great great movie, not especially well known, and an interesting challenge to the many heroic western myths that most western films embraced.