My In-Laws are vegetarians and use broccoli on pizza all the time. It does not work well to put it on the pizza raw. Here is what they do. Bring a pot of water to a boil. Have your broccoli cut up in little pieces like you would put it on your pizza, and then put the broccoli in boiling water for 30 seconds, take it out and drain all the water off. Just that little bit of cooking does wonders for the broccoli on a pizza. It keeps a little crunch in the broccoli, but it is not raw. cooking it any longer (over a minute) will make it mushy after it is baked on the pizza.
Hope that helps,