Context: MC is talking with his servant about the fact that when he was still a student like her, he also forgot everything the moment after the test was over.
G1: 昔、白蓮ちゃんたちと一緒に風鈴先生のところでやったはずなんだけど。こんなはずじゃないのになぁ
MC: あーわかるわかる。俺もテスト……試験がおわったら、その瞬間に全部忘れてたし
G1: ご主人様もなんだ！一緒だね～♪
MC: 喜んでちゃいかんだろ。いや俺も俺だけど
Can someone help me understand what he meant here?
Forgetting what you have learned is a bad thing.
So the scene is that G1 is happy to know that MC did the same (bad) thing when he was a student. MC tells G1 that it is not something she(?) should be happy about, and 俺も俺だけど means something like "well, I did wrong, too".
The intention of the whole phrase is "The fact I did the same thing should not be the reason you are happy about, (because the forgetting is a bad thing), but then the blame applies to me, too (because I did the bad thing)."
