What is it called when you defame someone and you happen to lose respect for doing that.
"George is verbally attacking John, by doing that George is losing people's respect"
George <blank> himself by attacking John
George shot himself in the foot by attacking John.
To do or say something that inadvertently undermines one's interests.
You could consider using the verb backfire which means:
(Of a plan or action) have an opposite and undesirable effect to what was intended: 'overzealous publicity backfired on her'.
Your example (You need to change the word order):
George's attack on John backfired on himself.
[Oxford Online Dictionary]
George undermined himself by attacking John.
ie, 'mining' under what respect you have, causing your own self to 'fall'.
George diminishes himself by attacking John.
George scored an own-goal by attacking John.?
The problem with "slinging mud" or even getting into a "mudfight" with someone is that you'll often end up covered in the same mud. In fact, it's so very likely, that the concept is specifically stated in the definition example...
Casting aspersions with intent to discredit.
The campaign degenerated into mutual mudslinging, each candidate trying to tarnish the other's reputation and looking bad in the process.
"Debased" : lower the moral character of (someone).
George debased himself by attacking John
There's an expression: "Whoever slings mud, loses ground."
It means that when you demean someone else, you demean yourself as well.
"Mudslinging" means insulting or attacking another person in order to harm his reputation or get him metaphorically dirty. "Losing ground" means falling behind in a competition, or being forced to move backwards. And it's also a play on words (mud/ground) -- when you throw something, you lose some of it.
So in this particular context, one might say "George is slinging mud and losing ground."
It's a third party opinion. How about simply "George made a fool out of himself by attacking John".
If you attack him publicly on this, you'll only be pissing into the wind.
George was digging his own grave by attacking John.
George is cutting off his nose to spite his face by attacking John.
"Cutting off the nose to spite the face" is an expression used to describe a needlessly self-destructive over-reaction to a problem: "Don't cut off your nose to spite your face" is a warning against acting out of pique, or against pursuing revenge in a way that would damage oneself more than the object of one's anger.
I think "poetic justice" or "poetic irony" fit the description.
"Dishonored", "Defamed" and "Disgraced" all mean the same thing. Take your pick.
Petard https://en.wikipedia.org/wiki/Petard George made a petard of himself by attacking John.
I Know this is old post, but just in case someone else stumbles on this like I did
seems to fit very well.