chrringoftheprintingmachine:

Tony Stark’s skepticism is born out of his life experiences.

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Tony ‘isn’t a team player’ and ‘doesn’t stick to plans’ not because of his ego or ‘narcissism’; rather because his hero (Yinsen) abandoned the plan & sacrificed himself thereby ensuring the safety of Tony’s own life. Tony is just following in Yinsen’s footsteps. He is trying to emulate his hero, and he is justifiably wary of people (even well-intentioned heroes) who emulate his antagonists.

In Tony’s personal experience, words have no weight. Promises change. There are already people who made promises of trust & being a team, only to misuse that trust and back-stab him. Ideals and ideas (even that of Avengers itself) can be corrupted. Hence, he doesn’t blindly accept slogans and platitudes offered. 

Because Tony knows the reality: An assertion does not a truth make.