It's really easy to be dismissive these days--because people talk a lot of shit.
There's probably no more dismissive group than founders--because you have to dismiss a lot of doubt and negativity on your way to success. However, a lot of founders have a tendency to be overly dismissive--to tell themselves a narrative and stick to that, no matter what anyone else, even if the criticism is warranted.
Sometimes, it isn't based on a lot of information--like when someone says you should be worried about a competitive product and a founder really hasn't even looked at it yet. Other times, the criticism comes from someone who doesn't know the founder that well, so the excuse is, "Well, they don't really know me."
Over the last couple of years, I've started practicing a very different response to criticism. I generally assume it's all true.
That makes me more open to it, and frankly, pretty vulnerable to letting some difficult to hear things sink in.
Then, I try to prove to myself that it isn't true--which I can do pretty easily most of the time thankfully. Going through that exercise keeps my actions well examined--and holds me more accountable.
So, if someone says I'm selfish, I look for ways in which I'm not to disprove that I am to myself. Sometimes, you wind up in a situation where you might not feel a certain way, but you don't have a lot of evidence to the contrary. Maybe I don't think I'm selfish, but I really haven't been doing much for other people lately or taking their feelings into consideration--so I've been inadvertently selfish even when I don't intend to be.
It's not the easiest exercise in the world, but I can't recommend it enough.