Incidents like this are common on both sides.

Our local news had a story on this just about two weeks ago. Some residents of
Medina (the posh waterfront community where Bill Gates lives) complained to the
cops that somebody was ripping out the "God Bless America, Reannoint George
Bush" signs from their front yards. One of the mega mansions caught the
n'erdowell on a security tape, and the cops got the sign thief.

To be sure they were giving equal time to both sides, they also ran coverage of
a Tacoma fire fighter who was arrested when he arrived at the Tacoma landfill.
Seems the back of his F250 was brimming over with Kerry/Edwards signs, most
with dirt still clinging to the picket stakes. Probably seemed like a good idea
about 2:05 the previous morning, just after the bars closed.

People are certainly emotional this time around. :-)

Did the guy with the three year old daughter expect to be welcomed with open
arms at the Kerry rally?

The same thing would have happened, and probably has happened at a Bush rally-
just slightly less likely because the cops usually herd all the anti-Bush folks
to a "protest zone" a few blocks away.