[huac]

There are procedures for this, everybody calls the observers of their opposing party 'thugs'

https://en.wikipedia.org/wiki/New_Black_Panther_Party_voter_...

https://www.theguardian.com/us-news/2016/nov/05/election-day...

[Karunamon]

Usually because there's a fine line between "poll watching" and "poll intimidation" and people generally aren't quite civilized, thoughtful, or well-mannered enough to stay on the good side.

That includes "shouting racial slurs" in your first link.

[tdb7893]

That's more worries about them harassing voters or legitimate election officials than not liking oversight.