Why should people not feel uncomfortable about talking about their sexuality or sex in general?
If we are going to make this argument (which many people would disagree with) we would say that people should not feel uncomfortable talking about sex and sexuality because that is a very natural part of human life. We can also say that if they are uncomfortable about talking about sex, they will pass that attitude on to their children and bad things can result.
Sex and sexuality are not dirty things. They are things that are part of natural human life. Because they are natural, we should not think that it is shameful to talk about them.
In addition, a failure to talk about sex can have bad consequences. If we do not talk to our children about sex, they will be naïve and ignorant. That can end up hurting them when they are teens and young adults. They might not know enough about sex and sexuality to handle it when they start to have sexual urges. This might end up causing them to engage in risky behaviors. This would be a very bad thing.
Thus, we should not be uncomfortable about this both because it is natural and because it can be very important to talk about such things.