There are a number of ways to answer this question. Not one is totally correct because there are many reasons for what you see.
Let me start by stating that I am not Catholic. I am Christian but don't claim any specific denomination. The theological response to your question would go something like this:
First, we must define what is meant by "love". The New Testament (the part of the Bible that states "love your enemies") was written in Koine Greek. This language was very precise. In the New Testament, there are two different words that were translated as love. The problem is that "love" doesn't accurately convey the intending meanings based upon the actual words used.
One word that is translated "love" is the word "phileo". The other word is "agape". Both words do mean love, but they speak of a different quality of love, not quantity.
Phileo speaks of a love that is based on familiarity. It is a love that grows hot and grows cold based upon how a person feels toward the one loved. It is more a feeling than anything else.
Agape, on the other hand, is not a feeling. It is not based on familiarity. It is a choice. It is a decision to do what is best for the one loved reguardless of how it will affect you. It is completely selfless. This love is always other-focused.
The word used in the verse you mentioned is agape. Why, then, do some Christians and Catholics "diss homosexuals"? This is a very good question!
On one level, it is because of immatureity of the Christian. On another level, it is out of agape for the homosexual. The immature Christian has trouble "seperating the sin from the sinner". We attack the sinner when we should be attacking the sin. We don't like to admit it, but the sin of homosexuality is no greater than the sin of lying, adultery, speeding, murder, gosipping or any other sin that, yes, we Christians, are involved in. We like to think that we are, somehow, better. But, we aren't. There might even be some fear that, if we acknowlede this, we will look bad. (We fail to realize that we already look bad!)
The other reason that Christains might appear to "diss" homosexuals is out of agape. The Bible does clearly teach that homosexuality is a sin. It seems to be most clear in the Geneva Bible. 1Co 6:9,10 says, "Knowe yee not that the vnrighteous shall not inherite the kingdome of God? Be not deceiued: neither fornicatours, nor idolaters, nor adulterers, nor wantons, nor buggerers, Nor theeues, nor couetous, nor drunkards, nor railers, nor extortioners shall inherite the kingdome of God." The word "buggerers" is an old word for homosexual. In the King James, the same verses say, "Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind, Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God." Here, we have a gentler way of expressing it, "abusers of themselves with mankind." Remember, however, that I have already pointed out that this sin is not special. It is not worse than any other sin.
So, how can a Christian "diss" a homosexual out of agape? How can a pastor refuse to marry same-sex couples out of agape? The Bible tells us that every Christian has the responsibility to show the world its need for Jesus. This is supposed to be done out of agape. To appear to endorse an act of sin (no matter what that act is) would not be an act of agape. It might be an act of phileo, but we are called to love our neighbors with the greater love, agape. To do this, we are willing to risk ridicule and hatred.
We, humans, have a difficult time understanding how to "seperate the sin from the sinner". It is hard to live a life that is accepting of the person but not condoning of the lifestyle. I am sure that many who read this will immediately think, "hypocrites". And, in some cases, that would be a correct assessment. However, in most cases (I hope) the truth of the matter is that we simply do not have the mind of Jesus. We simply cannot comprehend how to appropriately love these people and yet not condone their lifestyle.