Context: The character was sad and helped someone he didn't know. Here he explains his reasoning for doing so.
I'm a bit unsure of the actual nuance of 手前. My understanding after some googling it's that it's akin to 以上は?
The sentence should be akin to "I thought that by meddling with people I can also remove my own shame" phrasing.
In short, what is the actual grammar for た手前?