Regardless of the wording of the translation, it is obvious that the Bible is referring to homsexuality in some form or another. Therefore, homosexuality is wrong and your argument is bunk.
This is a very weak argument. As an argument it is almost worthless. Consider if the word for which there was no authoratative definition were in Leviticus 11 (which speaks of which animals are kosher to eat and which are unclean), and there was some uncertainty over what animal was the one that was unclean. Your argument would go:
Regardless of the wording of the translation, it is obvious that the Bible is referring to eating meat in some form or another. Therefore, eating [any] meat is wrong and your argument is bunk.
Which is clearly wrong, since those same verses list several animals that are kosher to eat.
In any case, the two most likely possibilities for the intentions of Paul, and the few Christian writers to also use the word, were that we understand
arsenokoites to mean some specific sexual offender, perhaps a "john," or maybe a pimp or some other more nefarious character involved in the "trade," or that we understand it as a reference back to the ban of Leviticus 18:22.
In the first case, we are back to the fact that banning pork is not the same thing as banning all meat. Calling people involved in homosexual prostitution sinners, is not the same as calling all homosexuals sinners.
In the second case, we need to examine the nature of the Levitical ban. Nowhere does the book of Leviticus indicate that there is a moral difference between the commands in, for example chapter 11, and those in chapter 18. While some of the actions forbidden in those chapters, and other chapters are labelled "wicked," and forbidden elsewhere, this is not true of the Levitical dietary restrictions or of "man-lying."
Except for possibly the two Pauline verses which use the word
arsenokoiten, there are no other verses which comment on "man-lying," and only one other passage to mention homosexual activity, Romans 1. In other posts, I mentioned that in Romans 1:26-27 the "evil" is not homosexuality, but uncontrolled passion, leading to indiscriminate indulgence.
All of which means that when God used the events chronicled in Acts 10, 11, and 15, and the arguments in Paul's works to nullify the Levitical ban on kosher food, and Sabbath blue laws, etc., there is no logical or Biblical reason that we should still enforce the "man-lying" ban. Indeed it goes against the teachings of Paul, James, and Jesus, himself.