Bad example. The courts (and general ethics and morals) dictate that there are certain areas everyone has a right to privacy, the bathroom, changing areas, etc.
The school routinely allows parents to film sports events, plays and presentations on school property without express consent from the participating students.
This was a school event on school property and would easily meet the same criteria as the examples above.
Next time think through your example.
NeverGore
A student who participates in a basketball game has no reason to care about being taped. A student who asks a question at an assembly about homosexuality has every reason in the world to fear his question being aired on the Hannity show. A student changing in the locker room is concerned about his own privacy.
The parent was not a neutral observer and the assembly was not a neutral assembly. This is why the principal made an issue out of student consent. It's a real concern.
People are wasting their time trying to make an issue out of a program which is popular in the town (Newton's pretty damn blue) and which parents can opt their kids out of.
Some backstory: Brian Camenker got involved in a state legislative race in my city a few months ago. By all accounts, his style of in-your-face campaigning HURT the conservative who was running and let the liberal waltz right into office. This guy thinks that mailing fliers that say "anal sex" 20 times on them will move voters toward his candidate. These people are less politically astute than Newt Gingrich and Bob Shrum combined. I know full well why the school banned them; they seek publicity for themselves in a way that HURTS the causes we all agree on.