That's too extreme. It's more correct to say that it's impossible to separate the competence of the hiree from race because AA makes race a factor in the hiring process in place of hiring based solely on merit. Thus it taints the hiree and all hirees of that race. Certainly many, if not most, AA hires are competent.
But race is at best a minor issue here although, it's become more of major issue especially on the right.
The race of Blair is the issue here because it is quite clear from the record that they were reluctant to fire Blair because of his race.
No. Garbonzo had it correct the first time. It is impossible to view an affirmative action hire as competent. They got the job only because of their race. This view will remain until they prove otherwise and will be reinforced or re-established if they mess up. In the minds of everyone who thinks, there is someone of a different race who was more qualified but who didn't get the job because of their race.
Note that the reality may be that the person hired was the most qualified candidate and is exceptionally competent at the position. The view will still remain that they are only a quota hire because of affirmative action.