You posted an unaccredited cut and paste
As far as grammatical analysis
"Arseno- means 'male' and can be either the subject or object of the action in question, gramatically as well as sexually. 'Koites' is a feminine noun meaning 'bed'; in the singular it can be used either literally as a generic 'bed' or figuratively, as in The marriage bed. In the latter case, it connotes sexual monogamy, among other things. In the plural, 'koitai', it is used to mean 'bedding around' [cf Rom13:13], a more appropriate term for promiscuity than 'inappropriate contenteia', which properly mean prostitution.
Combining the terms leads to saying that 'arsenokoitai' means literally, 'male fornicator' or really, 'promiscuous male' but this runs into some troubles. First, 'arsenokoitai' is a feminine plural noun! It could be this simply reflects that gender of the bed or it could mean the gender of the offending party. Either way your point disappears. If the former then we have a man going to a woman in HER bed
which is not homosexuality or in the latter the prohibition is against promiscuous females
"This is mistaken. The noun 'arsenokoites' is masculine, and its plural is 'arsenokoitai' (also masculine). It is wrong to say that the correct plural for masculine 'arsenokoites' is 'arsenokoitoi'. What probably confused you is that many feminine nouns (those ending in -a or -e) have a plural in -ai. On the other hand, many masculine nouns (those ending in -os) have a plural in -oi. But masculine 'agentive' nouns (sort of like English nouns ending in '-er' or '-or' like 'actor' or 'banker') have a nominative singular in -es, and a nominative plural in -ai. There are hundreds of such words. One common biblical word following the same pattern, for example, is 'mathetes' ('disciple'). The plural is 'mathetai', which looks feminine to people who have only a passing knowledge of Greek, but is really masculine. Or, from Classical Athens, there's 'dikastes', 'judge' the plural of which was 'dikastai', 'judges'."
Mixed plurals are always masculine; only when all members of a group are female can a feminine plural be used (if one exists).