Obviously this thread is very long and almost certainly all i'm going to say at this point is redundant, but what the hell.
Is prostitution "immoral" to you,
Nope, not in principle. Not as a general idea.
However, many if not most of the actual conditions in which it is practiced are very harmful to the prostitutes, which are mostly women. It can also be harmful to others involved. So there are many situations where i'd consider some of the things being done to be immoral.
That doesn't mean that these problems can't be addressed (but that's a more complex issue), and the prostitutes in most cases are not to be blamed for these problems. So when it comes down to it, if i know someone is a prostitute, i'd be mainly concerned for their well-being, rather than calling them immoral (even though it'd be possible they are doing some things which i would deem as such).
If i know someone who is a pimp, i'll be more concerned about what things they're doing which would most likely be immoral in my eyes, given the current conditions.
Mainly because i can't formulate any intelligent argument for why i should consider it immoral, and i have not seen such arguments made by others either, so far. Nothing seems to be
inherently harmful about it, despite of the harsh reality it often takes place in.