I don't think he was as terribly irresponsible as he was made out to be. He does know what he is doing, even if it seems a little eccentric to us. If I saw some regular person off the street doing the same thing with their child I would be concerned, but this is different.
Of course there was SOME risk, but not enough to be considered negligible. And if something had have gone wrong then there were other people in there too, and it could have been rectified.
However, while I don't think it was dangerous, I do think it was foolish. He did do it for at least some degree of shock value, and while he defends his actions by saying he needs to teach his kids to be around crocodiles, the kid was only a month old, and had no idea what was going on. So there was no real point in the baby being in there, and he should have predicted that there could have been some backlash over it. Was it really worth the publicity risk?
I do feel sorry for him though, he does seem to genuinely care about his kids.