This incident should never have been reported to the SS. It should have been squashed at the local level. ...Absolutely. 100% in agreement with you.
What the SS did is indefensible. ...In general, I'd agree with you. However, we weren't there. I (and I suspect you) would define a "walk through" as walking through my house, peeking in the pantry, and looking in closets for stuff to find. However, this guy might have defined a "walk through" as sitting on the front porch drinking a cup of coffee with the agent while they go through the motions of following up on a specious travesty of a complaint. Or he might have said, "I've got nothing to hide, come on in!". Who knows.
I'd further offer that everyone on the thread is assuming that the reporter who wrote this got their facts right. It's entirely possible that they're partially right, completely wrong, or this guy was misquoted, taken out of context, and so on.
Unless further info comes out, I'm willing to cut the Sec Service some slack. The PD, not so much.
The SS should not have been at the house in the first place.