I don't think anyone is disputing that it contains a lot of tomatoes.
However, it also contains a load of fat and salt too which standard "vegetable" vegetables don't and as the whole point of the 5 a day exercise is to reduce the intake of calories, salt and fat, this seems to compleely undermine it.
It wouldn't surprise me if fast food lobbyists had something to do with this vote.
Pizza is junk food, no matter what toppings you put on it, as the fact it has dough and cheese as two of the main ingredients makes it unhealthy.
Also not buying the cost argument, as vegetables are quite clearly much cheaper than pizza, especially in the US where they have so much arable land.