How much clearer does Paul have to make it that this is his opinion AND not a command from God?
It's difficult for me to imagine why are are so dedictated to justify prostitution, and having sex with people other than your wife.
Jesus - not Paul - Jesus taught that God, from the beginning, intended a man to be joined to his wife, and that's it:
Matthew 19:4-6 KJV
4) And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
5) And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?
6) Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.
Perfectly clear . . . 2 become 1, not, 3 become 1, or 8 become 1.
Paul taught to not be joined to an harlot, no "this is just my opinion".
1 Corinthians 6:15-20 KJV
15) Know ye not that your bodies are the members of Christ?
shall I then take the members of Christ, and make them the members of an harlot? God forbid.
16) What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh.
17) But he that is joined unto the Lord is one spirit.
18) Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body.
19) What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
20) For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's.
So you either obey this or you do not. And that's on you.