They're over ninety percent more likely than their unvaccinated counterparts to remain uninfected, in which case they will not transmit the disease.
The questions regarding reduced viral shedding among the infected but vaccinated, and how much that effects that population's transmission rate, is interesting but probably secondary, I would think. (I don't know quite whether those were all rhetorical questions or something you wanted a dissertation on :D )
Not against omicron, it basically ignores vaccines. Vaccinated people might be a bit less serious, but they still get ill and we have had many super spreader events among vaccinated populations where almost everyone exposed got it.
Vaccine might reduce spread a little, but vaccinated people spread it so much already that it can't be anywhere close to 90% not spreading.
Omicron increases vaccine escape rates from about 5% to 30% which is bad, but not ignoring vaccines.