First of all, we need to remember that God is genderless. God does not have genitalia. God does not have x and y-chromosomes. God is neither male nor female. You say that God made nature “perfect” with only two sexes. I am not exactly sure what that means. We can argue that nature is not absolutely perfect. God said that it is good (Genesis 1:36). In fact, it is very good, but it is not perfect. Only God is perfect. the fact is that mutations happen and there are genetic imperfections in nature. In nature, sexual reproduction is important so that species can evolve over time. Species which undergo asexual reproduction cannot respond nearly as quickly to changes to the environment over time. So, in nature, “sex” exists because of its positive contribution to the health and evolution of species. I am not sure that the Bible ever says that we were created perfect, and I am not sure that having two sexes is part of making us somehow more perfect. Given that God is perfect and God is genderless, I am skeptical that having two sexes is an aspect of perfection. However, it is clear that God created humans male and female, and that our complimentary nature helps to complete one another. It also allows us to have a kind of mystical union in the marriage relationship. I know nothing particular about why there could not be a universe with more than one gender, but I have no way to even speculate about that.
Now, let me get to your questions. How should we act toward hostile feminists? That is easy. We should love them. That is what Jesus would do. Why are certain women hostile to men? Probably because they were treated badly by men, and that is on us men, I would say. So we (especially we men) had better love these “hostile feminists,” and we had better apologize to them for the terrible way some men have treated them. Maybe if we love them enough, we can help them to overcome their hostility.
How should we act toward LGBT supporters? That is an easy question as well. We should love them. We should show compassion to them. I am sure Jesus would have hung out with them, had dinner with them and reached out to them. He would not have judged them as some hypocritical Christians do. He would show them love first, as he did the woman caught in adultery in John 8, but then, after showing his love, then he would have told them to go and leave their life of sin. But let me tell you, LGBT people are no more sinful than you or me. Let us show them the love of God and perhaps we can help them to come into God’s family.
Is intersex the third sex? The answer is a very solid no. There are two sexes. There are two genders. There are people with two x-chromosomes. They are female. There are people with one x and one y-chromosome. They are males. This is the way God made us. By the way, there is a very small minority whose gender is somewhat undefined. There are people who are xxy, xyy and xxx. These people need our compassion and help. There are also a quite small number of people who, even though they are either xx or xy, have physical characteristics that are not fully developed as male or female for one reason or another. This is a real medical condition. These people also need and deserve our love, our compassion and our understanding. The last thing they need is for us to ridicule or accuse because they are not fully normal as to their gender. We can assume that Jesus would have shown love, patience and compassion to this small minority of humans whose gender is not fully developed. However, “intersex” is not a reference to a scientifically identifiable category and, no, it is not the new gender.