Adding something derogatory about yourself when you disparage others does not mitigate the fact that you have spoken loshon hora.  This includes instances when you mention that you and a friend both did the exact same action or have the same fault, and you begin by talking about yourself.

For example:

“Ben and I shoplifted when we were younger.”

“Nobody in our group studies Torah Properly.”

“I don’t give enough charity, but neither does Mr. Stern.”