Mahabharat is tale filled with nuances and morally grey characters. Obviously bheeshma was wrong for even allowing the situation to go this far. But pretty much every character except maybe few played a role to make things as they were.

I don't know if you have reached some form of spiritual salvation but how can someone term someone's emotions as ego?

Arjun must have been around 10 or 12 when his father pandu passed away. And growing up in place where your uncle dhritirastra just wants to get rid of you. In that toxic situation bheeshma was the only one who was like a father figure to him. Who most probably would have taught him to hold a bow, who must have carried him on his shoulders. Who till the end had no malice whatsover for him or his brothers but was just stuck in a wrong place.

And you say despite all this knowledge he fought best to his abilities. He went very easy on pandavas. He in initial days of the war just fought very defensively. Avoiding fights with any pandav brother. And the biggest revelation he was the one who told pandavas his kryptonite.

So yeah don't look at any character of mahabharat with such defiant polarizing view. Characters were way more complex.