Putting the legal issues aside, if a job applicant told the employer that he/she was engaged in any immoral activity, the employer SHOULD be allowed to take that into condideration when making a hiring decision. Most employers look for employees of good character as well as those that have good skills.
I’ll tell you what would be a red flag for me in the above paragraph: a candidate who offered inappropriate personal information during an interview. Here are some highly inappropriate themes for a job interview:
~sexual orientation
~past mistakes (bad choices) that are not an issue for this job (such as, having had a child out of wedlock)
~age
~religious affiliation – unless the job is a religious environment, such as a diocese, parish, religious school
~personal hobbies unless directly relevant to the job and illustrated by the candidate as a form of experience or expertise for this job (photography, for example, even in some cases reading habits which may shed light on a level/length of interest in the field). Other than that, what you do in our spare time (good or bad, moral or immoral) is not a subject for a job interview.
~personal tastes, such as spending habits, favorite TV shows, other personal preferences
~marital status: in itself, and without a context for the job, this is not conversational material
IOW, the same information you should be eliminating from your resume is the same information that should neither be offered at a job interview nor introduced by an interviewer.
And I would have a hard time justifying, if an employee later revealed “immoral activity,” firing that employee unless
(1) the immoral activity were a reportable activity (crime). Crime rises to a different level than private immorality. Someone who admits promiscuity is not the same thing as someone who admits commercial promiscuity (prostitution or pimping). Someone who plays The Lotto irresponsibly & recklessly is not the same thing as someone who admits illegal forms of gambling, including conspiratorial gambling (cheating).
or
(2) the employee brought conversation about the activity into the workplace, affecting the office atmosphere and distracting him from his professionalism or performance
and/or
(3) the employee brought the activity itself into the workplace. (Phone calls on the job related to gambling activity; internet searches for dates, and phone calls about those, during work time)
So again, discretion is a huge consideration to me when I do interview. If you have not the judgment to leave your personal life behind you, both at the interview and later, at work, then you would not be “an ideal candidate,” haha, to me. Whether you are heterosexual or homosexual.