What is it called when someone attacks a person and the offender gets an even worse reputation?

What is it called when you defame someone and you happen to lose respect for doing that.

For example,

"George is verbally attacking John, by doing that George is losing people's respect"

Thus:

George <blank> himself by attacking John

Solution 1:

George shot himself in the foot by attacking John.

To do or say something that inadvertently undermines one's interests.

_TFD

Solution 2:

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]

Solution 3:

George undermined himself by attacking John.

ie, 'mining' under what respect you have, causing your own self to 'fall'.

Solution 4:

George diminishes himself by attacking John.

Solution 5:

George scored an own-goal by attacking John.?