There is a world of difference between loving someone and having sex with someone. Our culture has so merged the two concepts that we have derived the term "making love" to describe it.
Where loving another is perfectly good, having sex with him or her can be wrong.
A person might love someone he is not married to and not sin, but fornication (sex outside of the marriage relationship) is a sin. To have sex in such situations is anything but love, because if you love others, you will not encourage them to sin. The truth is, you love yourself more than you do him or her, because you are satisfying a fleshly, emotional need at the expense of his or her soul. How is this love?
It is possible to love another's spouse and not sin, but to covet and "make love" (i.e., have sex) to another's spouse is adultery. You will contribute to ruining a marriage, ruining a family, ruining lives and condemning souls. How is that loving your neighbor? How is this loving God? How is this love? "Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge" (Heb. 13:4).
Loving a person of the same gender may not be a sin, but lusting after and having sex with them is homosexuality. This is a sin (1 Cor. 6:9-11; Rom. 1:24-32, et al). God created the marriage relationship for a man and a woman (Gen. 2:24; Matt. 19:4-6). Regardless of what men may declare, God created the relationship and gets to determine its bounds. The problem with homosexuality is not loving (in its purest form) another human being, but having sex with them. Two homosexuals might love one another, but how is this love in light of the cost to their eternal soul? How is a man having sex with another man or a woman having sex with another woman love as God designed it? Love and sex are not the same thing.
Frankly, we all have our lines when it comes to sexual sin. The lowest of the lows, even among criminals, is pedophilia. Yet, this too is a sexual sin. Some argue that because it is non-consensual with minors, it is wrong. The scriptures make no such distinction. It is wrong because it is a sexual sin outside the designed realm of marriage. It is heinous because it preys upon innocence. Yet, because one is naturally inclined or has that sexual preference, even if they call it "love," does not make it right. It is wrong, period. There is no love in pedophilia, only evil and sin.
In order to embrace any of these sexual acts as good and acceptable, one has to fundamentally deny and categorically reject God. We have to call good, evil and evil, good. "Woe to those who call evil good, and good evil; who put darkness for light, and light for darkness; who put bitter for sweet, and sweet for bitter! Woe to those who are wise in their own eyes, and prudent in their own sight!" (Isa. 5:20-21). We have to decide our ways are better than God's ways. "For My thoughts are not your thoughts, nor are your ways My ways,” says the Lord. For as the heavens are higher than the earth, so are My ways higher than your ways, and My thoughts than your thoughts" (Isa. 55:8-9). Make no mistake—we must renounce fundamental truths and believe humanistic lies to rationalize fornication, adultery, homosexuality and pedophilia as good, loving activities.
You might readily dismiss what I have written here as mere Christianity, but lets not fool ourselves into thinking that "Christians" can support such and still be followers of Jesus. You have the right to deny God. He has given you that choice, but not with impunity. Whether you choose to believe the Lord or not, don't mistake sex for love. Even basic logic tells you that the two are entirely different acts.