Following exes on social media

So a while ago my boyfriend didn't like how I had guys on my accounts so I deleted all the ones with past history cause yeah I understand it's past so past should be past but recently I found out he still friends will his ex on Facebook and Instagram and she's always liking his post and when I asked him about it he said it's cause there relationship didn't end bad and I told him so it's ok for u to have past on there but not me and I guess he got the memo and deleted her but should I have been mad about it or just let it go what would u guys have thought about this