On the other hand, if they had to face living to see the consequences of their actions they would have some motive to not shit everything up.

One would hope by the time a conversation on human immortality becomes relevant, society will have found a way to limit the damage such a person could do.

Wishful thinking I suppose.

I’m a bit scared to imagine a 700 year old politician

I imagine it'd look a lot like the groups that have been pushing the same issues for a long time - i.e American evangelicals trying to work God into the constitution for the past two centuries.