I can kind of see where Kirr is coming from. The issue is somewhat of a moral issue and one of personal character. Miranda's decision to abandon her family to pursue her career speaks little as to her moral character. It says that she is willing to have babies but not take up the appropriate responsibility in regards to them. She could have resigned her commission but she puts career above family and that is what I think Kirr was saying.
I too think it's a bad choice and even if it was a male character I would say it's a bad choice. Having children is something that requires personal sacrifice. You can't just choose when you're going to be there for them and when you are not. I don't see the comparison to the military as valid either because military are not deployed for years. Months yes but a Starfleet vessel could be years out and yet she chose this. I personally cannot understand any mother who would do such a thing to their child. It seems cruel and unusual to both the husband left behind and the children he now has to raise alone. She might as well not even be married to him. With all the statistics there are that show children being raised in single parent households contribute to more crimes than any other demographic I cannot see how a Star Trek author can in all good conscience support such a position and say it's OK.