I would call his manner overbearing, disrespectful, and inappropriate.   Children have have childish behavior, and that's not what the passenger displayed.   What he displayed was a blatant sense of entitlement and disregard for others.

The logical fallacy in your argument is that you are saying his "childishness" resulted in him "disregarding" the rights of others, because that is what he did.   People have, and the law supports, an expectation that they can conduct their business and activities in public places without being harassed or molested, not even "just" verbally.  

Failure to respect the rights of others is what people should be looking for and seeing as the core wrong in situations, but very few are able.  It is not true that such failure to respect the *rights* of others is a side effect of something more acceptable or more understandable, like immaturity.  Failure to respect the *rights* of others is core to all human wrongdoing and evil.