As most have already said, as long as you haven't accepted them yet, you should be fine as long as your decision follows the Fair Housing Act (meaning you're declining of their application is not based on Race, Color, National Origin, Religion, Sex (including gender identity and sexual orientation), Familial Status, or Disability). 

I don't want to be responsible for putting strangers together and any problems that may occur between them, sexual harassment being top of mind. 

"A perception of a person's race, color, religion, sex, sexual orientation, marital status, national origin, ancestry, familial status, source of income, disability or medical conditions, or a perception that a person is associated with another person who may have any of these characteristics."

People are frequently accosted for their race, sexual orientation, or just looking like you have a few dimes to your name.

I doubt it's much better here in the US, everyone I know to be adopted, that are females have told me horrific sexual abuse stories.

So for me, that would probably include violent assaults, sexual crimes, murder, arson, most theft felonies, most drug trafficking felonies.

The day before that offer was going to be submitted, I was served with a summons for a lawsuit related to comments made on Facebook about an alleged sexual predator in my community.

Sexual assault.

Back in the 1960s and 1970s, these bans were present in most states and vigorously enforced as the sexual revolution of that era unfolded. 

According to a 1993* survey of 150 U.S. and Canadian medical schools, for example, only 14 percent of modern oaths prohibit euthanasia, 11 percent hold convenant with a deity, 8 percent foreswear abortion, and a mere 3 percent forbid sexual contact with patients—all maxims held sacred in the classical version.