Well, no wonder.
I removed the blade from my miter saw. It was, evidently, the original. Although it was carbide tipped, the teeth were choked with pitch and there was something - plastic? paint? - smeared in concentric circles on one face. Ah, yes. This saw had been used to cut Pergo laminate flooring over a decade ago. The only use since has been feeding it the occasional 2x4 (the picnic table being the last project to use it).
Gee. Why would a filthy, forty-tooth Sears blade ever result in tear out when cross cutting oak?
While I'm learning how to clean up a circular saw blade, I decided to actually get something that (I hope) is up to the task. A 90-tooth Diablo high ATB blade.
When it doubt, blame the tool and move on. If anything, use it as excuse to buy better tools.