I find this line of thought to be a bit too reductive. "Women's experiences and knowledge are disregarded because of their gender" is accurate, but not as informative as it could be. The primary causal mechanism underlying the problem is the creation of gender roles and expectations. The existence of gender roles and corresponding expectations means that certain domains become seen as women's areas and men's areas. When discussing matters that fall into the domain perceived as belonging to the opposite gender, an individual's experiences, opinions and knowledge will tend to be disregarded or given lesser weight. So, a man can and will experience a similar type of discrimination in a realm perceived as belonging to women, such as child care. This is one of the things that is meant when we say that "the patriarchy hurts men too," but we often don't explore the implications of that statement in sufficient depth.

All of the preceding brings us back around to the issue of "mansplaining". While it is accurate to say that men exhibit a tendency to explain things to women in a patronizing manner, I don't think the appropriate corrective action when one is facing this problem is to respond with an insult or rebuke (as "mansplainer" is commonly used).

I have also, though far less frequently, seen the term used in the context of suggesting that all men are incapable of being feminist or understanding issues affecting women. I see this as another form of associating an area of knowledge with gender, such that feminism is a woman's area where it's acceptable to discredit the knowledge of a person based on his genitals.