Cops are government officials too and as big government has grown the dangers of abuse from them have also grown. If you don't believe that the abuse of power by cops is a problem in the U.S., go to youtube and you will see many examples such as the tasing of a 72 year old grandma who was tased for asking too many questions.
If you're looking to make a point on constitutional grounds, I would contend that the real problem here isn't that Gates was arrested, but there is even such a thing as a "law enforcement officer" whose mere existence is an abrogation of the responsibilities of free citizens.
It's no coincidence that there are parts of this country with almost no law-enforcement presence at all -- and they have no crimes, either.
Why would you assume that someone who took the time to review the facts of this case and concludes that police have the right to investigate burglaries would also have to believe that police have the right to taser old ladies? One is okay, and the other is not.