Without looking at the specific case(s) mentioned in the linked chat, I see this behavior as positive. SE sites, especially SO, generate a tremendous amount of content. Since we allow anyone on the Internet to submit that content, some of it will inevitably be garbage. Every user with close vote privileges is responsible for cleaning and curating to keep our communities useful, and we should make that job as painless as possible.
The important thing here is that you can't force anyone to cast a close vote; you can only encourage them to visit questions with the suggestion of voting to close. If they disagree with you, they may just as easily upvote, or bookmark it for possible later reopen-voting.
Of course, it's possible to take this too far, but that's no reason to ban it. Every tool in the world can be abused. The proper response is to try to change the abusers' behavior, not ban tools.