I think "assholes" might be people who personally care AND practice direct challenges, but do so in a way that shame and blame individuals. Calling out mistakes is fine, as long as you don't assign biased blame to the person making the mistake. Startups are already difficult endeavors without the added pressures of being directly on the hook for a mistake. Teams should accept the suffering from an individual's mistakes with the assumption mistakes will be made by team members. If a given team member makes too many mistakes, then perhaps a review is necessary, but otherwise, it's a team mistake which can be learned from and used to improve the team and product.