It's meant to be a slap in the face to those Democrat/Catholics who like to toss their vows, write a check, and carry on.
See, that's the problem.
There's lots of Catholics who are not Democrats.
The annulment process can take 2 years or more for most people.
No matter how hard/easy/right/wrong it is to get an annulment, it has no bearing on the legitimacy of the children, and that is the fact. The children are irrelevant to the discussion. In fact, the annulment is irrelevant. It was his ex that sought the divorce in the first place.
If you want to call Kerry a bastard, just call him a bastard.