“לא תחללו את שם קדשי,” the Torah says do not profane my Holy name. This is the prohibition of creating a Chilul Hashem. The Chofetz Chaim goes on to explain that lashon hara is a chillul Hashem because it is done out of spite, not because you are over come by any physical desires.
What he means is that Hashem, when creating us, purposefully gave us physical needs that must be handled like eating, sleeping, cohabitating, etc. Hashem expects us to c ontrol these physical needs and use them for the sake of serving Him. However it is possible that if we are lax, those physical needs could start to control the person and he or she might start doing things unhealthy or even sinful, however that is not called a chillul Hashem as long as it does not become too habitual because Hashem gave us these physical desires and it is understood that it is an on going process to create a healthy balance. That doesn’t mean it is wrong if misused, it is just not spiting Hashem.
But if one slanders another human being or swears falsely even for the sake of making money, or even if this negative speech is said for the sake of defending one’s own honor that is still a chillul Hashem because no physical desire that Hashem gave him got the better of the person to cause him to sin, and even if it was for the sake of profit or honor, one has to always be attuned that Hashem honor comes first and if he doesn’t that by definition is a “slap in the face” to Hasham, lihavdil, and that is why it is a chilul Hashem.
We also saw that it is common place that lashon hara has a death spiraling effect, that once one starts slandering, even someone rebukes him for doing so, he’ll find excuses of why it is not slander in this case and will continue to slander the other person even worse which is the opposite effect of a typical sin. If a normal Jew ate a piece of pig unknowingly and then was told that it was pig he would not just take another bite, he would throw it out, rinse his mouth out and stay far away, but by lashon hara there seems to be the opposite effect and that is also why it is such a terrible chillul Hashem.