The biological reason: Someone with an internal process of decision making will likely feel questioned by someone with a verbal process of decision-making
Although this is not the case for every guy, the male brain in general is wired to process things internally before talking about it. Which means by the time a guy says anything (“Let’s fix the transmission and keep the car”), he most likely has spent quite some time thinking it through in detail. In his mind, this is a conclusion; a decision with a lot of thought behind it. He may not always be 100% confident in his decision (see Emotional Reason above!) but in his mind, it is an actual decision.
The problem, of course, is that most women (although, again, not all) are verbal processors, which means that a verbal statement is not a conclusion or decision. Instead, it signals the beginning of a conversation that is a crucial part of thinking things through in order to make a decision.
You can see the train wreck coming, can’t you?
When our man says, “Let’s fix the transmission,” he is conveying a decision into which he put some serious thought. But that announcement is the first we have heard about it! So we ask questions and raise all sorts of issues, because that is how we move our thinking along and eventually reach a thorough decision. Yet for him, our spontaneous verbal feedback can easily come across as “picking something apart.”
More dangerously, because we sometimes casually throw around language like, “Well that’s silly, we should just do it this way,” we can, without meaning to, tell him that after a full day of thinking something through, his conclusion was “silly.”
Either way, he feels disrespected and inadequate. It is painful. And that is why he gets upset and shifts into silent mode.
So what’s the answer? If you are a verbal processor and an inquisitive person, what will allow you to be yourself and ask the questions that you need to ask, without feeling like you are always walking on eggshells—or are at risk of hurting your man.