But it is a weak characterisation because you can construe basically anything anyone has ever done to be a selfish action, and in this case the evidence isn't p

But it is a weak characterisation because you can construe basically anything anyone has ever done to be a selfish action, and in this case the evidence isn't particularly strong. It's not like the whole essay is telling you to act in PGs interest. Basically you're assuming selfishness because in one possible interpretation of one sentence, it's possible for PG to derive any benefit at all. I don't think it's even possible to write an essay where that's not the case.