That's why Jon went to speak to he, to gauge her mental state. He didn't go with the express idea of just killing her; he was going to access for himself before acting - and after seeing her speech and speaking to her directly, he felt she was heading down the same path as the previous 'mad' Targaryen. If he tried to curb her, he risked ending up on the executioner's block for treason. Plus Daenarys was already shaken as she knew he had the better claim to the Iron Throne via his linage; so she might be quick to pull the trigger on him even if he said nothing. They no longer have a Dragon behind them and killing Jon woukld enrage Sansa and the otghers in the North, plus their allies. No disagreement here. In fact I thought Bran was more an 'eternal spiritual being' like the one he replaced, until they brought him back for the whole "Night King" fight. ^^^ That's true of any sprawling series (Book or TV) with a s**tload of characters.