NOx (and PM) is a local, temporary consequence. Catalysts exist to remove NOx out of exhaust gasses. They are perfectly serviceable.

Carbon dioxide is a permanent, global issue, where no (large-scale) capturing/cleaning methods exist.

NOx removes itself out of the atmosphere through natural means, CO2 does not.

You can close the cycle, hence 'ignore' CO2 emissions since they cancel out, and deal with NOx using today's existing technology. Same thing for PM and sulfur.