The users whose posts are getting deleted have done nothing wrong. We are simply doing some cleanup and deleting a private category that is no longer needed.
Yes, whether it’s a bulk deletion or using the delete button directly that number will increase.
The deleted posts count isn’t the best indicator of “good” or “bad” — more of a hint to investigate further (if you click the count you can see the deleted posts)
Here on Meta for example, I have many deleted posts through various cleanup efforts
I’d say that (at least in Western culture) red is inescapably bad. If you used green I’d be inclined to think, “Look at all the unnecessary things cleared away!”