A TV pundit's job is not to make excuses for bad calls -- it is to criticize them. Can't blame ol' Howard for doing his job.
And to add to that, two things:
1) Our primary complaint on this site is that pundits are too often clueless about the LOTG and the reality of managing 22 men on the pitch and countless others off it. Howard Webb has that experience and can use that experience to criticize poor decisions of referees better than can anyone else in the commentator's box.
2) "I didn't see it" really isn't an acceptable excuse at any level of officiating, least of all the Premier League. Our job, as officials, is precisely to see it and deal with it. If someone hasn't seen something, it's likely because they made a poor decision prior to the event (in terms of positioning or focusing attention at the wrong spot) and they need to recognize and do a better job of that. That the television people have access to multiple angles isn't really a useful argument because you only need one angle to know that you've made the correct or incorrect decision. The ref's job is to make the right call. If he hasn't, then I see no reason why criticism shouldn't be leveled against him.