Just point out the attack vectors, with some reference on solving those. No need to "you're implementing things yourself. bad. use someone else's library". Tha

Just point out the attack vectors, with some reference on solving those. No need to "you're implementing things yourself. bad. use someone else's library". That is gatekeeping indeed, and a rather insulting way to express your concerns. If you simply demonstrate the complexity of dealing with all security concerns, they'll realize what they need. Prepackaged "always do this" does not teach well.