The issue is not whether they should have checked it out or not. The sign itself should have given them a clue and certainly a check of police files and lookout lists would have sufficed. The fact that they felt it necessary to have a walk thru of the individual's house to determine if he was a member of some undefined "hate groups" should send shivers through anyone who believes in the US Constitution. What the SS did is indefensible.
And who in the police department was responsible for reporting this to the SS? Is this a rogue officer or a flawed policy within the police department? This incident should never have been reported to the SS. It should have been squashed at the local level.
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.