Opinions on the lack of open-mindedness of Dota players.

Far too often, I see Dota players who immediately dismiss their teammates on the basis of disagreement with the gameplay decisions their teammate has made.  They will condemn and rebuke their teammate's choice of items, spec, lane, etc, without giving any thought the idea that their own conceptions of what is viable/unviable may not be based on perfect information.  Such a hostile reaction is doing far more harm to your chances of success than the choice your teammate has made.

Everyone comes at a game of Dota with a different set of experiences that have influenced their playstyle.  If you have played consistently in the past with a victory-oriented mindset, and you are not currently in low priority, there is a good chance that the people you are being matched with are also aiming to win the game.  As such you can make the reasonable conclusion that despite your impression of their decisions, they are most likely making them in an attempt to win.  Now, I am not here to dissuade player's from giving advice to teammates, but I am trying to dissuade pre-emptive dismissal of teammates.

When you begin a game, there are a lot of unknowns.  Since Dota relies heavily on team play, not knowing your teammates is probably the biggest source of concern for most players.  When you see a teammate who has made what you consider to be a bad decision, and you immediately rebuke them for it, that teammate will use that limited interaction to categorize you as hostile and will probably respond with hostility as well.  Now you have two players on the same team who hold poor opinions of each other.  They will be distracted with typing and they will hesitate to make sacrifices to aid each other.  The whole team suffers as a result.

Now unless the decision they have made is clearly intended to lower your chances of winning (ex: feeding), the best response when you disagree is to either ignore it, or comment in a constructive way, perhaps offering an alternative.  Your teammate may agree with your assessment or they might not.  If they choose not to alter their gameplay, the best thing you can do is to adjust your own gameplay to work around what you see as a potential problem.  At worst, your teammate will contribute to a loss, but after that game you will probably never see them again.

However, there is always the possibility that the decision they have made is actually a good one, but you are lacking information that would allow you to understand why.  In this case, if you rebuke them, they will view you as inexperienced due to your lack of understanding of their strategy, and this may also lead to hostility and a breakdown of team play.  If you just go along with their decision, you might learn something that will allow you to improve your own game.

TL;DR
If your teammate is doing something you disagree with, you're better off just dealing with it than responding with hostile commentary.  If you must say something, keep it constructive, and be prepared to accept that they might not change their mind.