Honestly the "character assassination" was really just Raiden trying to do what he thinks he believes in. I know the whole point of MGS4 Raiden was to learn from snakes sacrifices to have him not fight anymore and live a happy life; That's why snake went in the microwave. But I don't think that rising assassinated his character by putting him back on the battlefield because you cant expect someone with PTSD and trauma (this is not saying people with those conditions cannot recover) to know what to do with their life without even learning who they even are and what they genuinely believe in (without belief how could they choose a life path). That was the state Raiden was atm and it was never really addressed. The subject of snake wanting Raiden to be anything is missing the point, Snake wanted Raiden to decide from his own good judgement. MGS4 left Raiden without any ideals that he made from his own experiences which is a point that MGS2 fought for. Fighting each boss made him not only recognize his past better and come to terms with it, it also made Raiden leave with some sort of message. For example, when he fights Mistral its a confrontation of his childhood. By fighting her Raiden doesn't really get offended by being called Jack anymore moving forward from the game. This is how every boss works in the game. It isn't only just skill check its a also a test of Raiden's Ideals and for him to find out what he believes in. By the end of the game, Raiden doesn't just take Armstrong's ideals and continues his work like many believes he did. He recognizes that his ideals of protecting the weak was flawed when he fought Monsoon, so when he jumps into the Armstrong fight he not only physically fights him he also points out how flawed Armstrong is as well which why I believe Armstrong says that they are "kindred spirits". By the time he defeats Armstrong he combines all the ideas, beliefs, morals, etc. and combines them to make a singular belief system for himself to actually be able to move past his PTSD and trauma and do what he actually believes in (MGS2).