The 9th Amendment does not guarantee a right to sodomy or adultery. Both crimes were very strictly punished by all the states at the time of the adoption of the amendment.
The notion that you are free to do what you will so long as you don't violate the rights of others is fatuous. Society has always placed restrictions in this area regarding bigamy, adultery, polygamy and polandry, prostitution, staturoy rape, homosexual conduct, bestiality, and similar.
Don't get me wrong. I do think that homosexuality is an abomination in God's eye. I just don't like the measures that the government would have to take to enforce laws against it.
The enforcement of the laws would not be through the government snooping in your bedroom, but from sworn complaints by people who are victimzed by these acts, or if the police would observe somebody performing these acts in public (such as homoexuals at rest stops and public bathrooms).
We need to move beyond the childish idiocy that sees a government agent peeking in your bedroom at night to ensure you aren't comitting adultery. In the real world, it will be your spouse, not the government, who swears out a criminal complaint against you.