Terms like 'enemy combatant' are used to de-humanize, even though they have legit meanings. They are much more loaded than dry words like 'target'. The word 'target' is the end result of a process, resulting in specific actions against a person. One does not become a target until after the process has ended.
The word 'enemy combatant' otoh is a label which is applied at the beginning of the process, and which justifies everything in the process. That makes it much more dangerous and insidious than 'target.
If I label someone an enemy combatant, and you are a good patriot and take me on faith, then you don't care about what I do to him or how he is treated. He is a dirty enemy combatant after all. Enemy combatant is a word that is used to dehumanize someone so that average people don't object to his further treatment. If we looked on all of those people as humans, implying they should be treated as humans with rights, innocent until proven guilty... that would be inconvenient for the people on top who feel they should be able to treat them like cattle.
I think that the truth lies somewhere in the middle of the two arguments.
It is certainly common for soldiers to develop demeaning terms for their enemies. This is an attempt at separating them from oneself which would allow an easier time to kill them.
However, I think the use of the terms enemy combatant and target have very legitimate uses. Enemy combatant is used as a legalistic term, as the group which the U.S. is fighting is unique in modern legal linguistics. They had to call them something for legal purposes due to the fact that, at least according to certain legal minds, they did not fit any of the current classifications.
By the way, I don't think adding "combatant" to the word "enemy" makes them any less human then using solely the term "enemy".
In terms of target, it is usually seen as a goal. "We have reached our target destination," or, "We have reached our monthly sales target." Remember, especially when it comes to military communications, references tend to be coded, so as not to identify to the enemy what the actual goal is. So if the goal of an operation is to kill or capture a specific person, for secrecy's sake, the use of the word "target", or their appropriate specific code word, is used. Hell, every U.S. President since Truman has had a code name used by the Secret Service. Does this de-humanize him?