As much as I hate OregonLive, they have the full AP story on the event here.
To sum it up: three teachers walked in wearing shirts that said "PROTECT OUR CIVIL LIBERTIES". To quote the AP piece:
"Three Medford school teachers were threatened with arrest and escorted from the event after they showed up wearing T-shirts with the slogan "Protect our civil liberties." All three said they applied for and received valid tickets from Republican headquarters in Medford.
The women said they did not intend to protest. "I wanted to see if I would be able to make a statement that I feel is important, but not offensive, in a rally for my president," said Janet Voorhies, 48, a teacher in training."
So yes, apparently the rally security people thought that the message of protecting our civil liberties was an offensive, arrest-worthy one. I... well, I don't think I can make a comment that really adds anything worthwhile to the discussion. They were threatened with arrest for supporting civil liberties.
My head hurts.
Here's an article about it that includes a pic of the three teachers and their shirts. One commenter asked what was on the back of the shirts, and I'm curious about that too, but I haven't been able to find any other info on it. 4 years ago I'd have written it off as paranoia, the protestors manipulating the media or something, and I'd be sure that their shirt-backs would say "Fuck Bush!" or something similar, and to find out that they'd been burning him in effigy and beating Republicans with bats. But nowadays? I wouldn't be surprised if their backs were blank and if they had just been standing there quietly listening.