While it's true that nobody else is responsible for one's behavior, or even for the way one behaves when someone else "does them wrong"; it is not true that there is no such thing as being able to blame some others for some problems in some lives. As an example I'd use a perfectly mentally capable/sharp, but very elderly, individual who has to deal with younger people who are clueless and who think they know better than the older person. (OR, who don't understand the older person because they haven't lived with what he lives with).
After awhile, if the older person never gets a break from such clueless people, there's going to be a time when he reaches a saturation point and just writes them off, ignored them, gets nasty, etc. What doesn't help is the over-confidence of someone like younger family members who not only think they know better than the older person, or else who don't understand the older person knows better than his choices may APPEAR to indicate; is that with the unfounded and inappropriate "all-knowing-ness" of the someone like a younger family member often also comes an arrogance (and even mild aggressiveness) of youth (or middle age).
Point is, it's possible to drive someone to less than the best or the friendliest behavior after enough time goes by.
There are a bunch of rules that most people learn to live by (or try to live by) when they're young; and if they have the luxury of never, ever, having someone else screw up something in their life (or otherwise create problems for them, like that younger but clueless family member who makes life miserable and lonely for the very elderly, but sharp (or mostly sharp) older one; then all the rules apply, and the naive or uninitiated get to live under the false impression that they always do (as long as someone knows them and follows them). What's arrogant, too, is that far too many people think they're only ones who know and care about following all those "rules to live by".
Of course, someone like that very elderly person in the example knows that the people in question don't mean any harm; so what happens is they don't want to say anything to hurt the other person's feelings. OR, what else can happen is that if that younger person (caretaker, grown child, whoever) has it in his/her head that he knows better than the very elderly person; nothing the older person says will be taken seriously anyway.
This is a common and simple example of how some behavior actually can be/should be blamed on someone else; but life is full of all kinds of other examples of one kind or another.
AND, the thing is, when someone else makes a mess in a person's life whoever makes that mess isn't going to be all that ready to recognize it and own up to it.