Not sure where you live, but in the U.S., this is not the case. No landlord can discriminate based on race, age, children, and some other things. When I was in college, there were adults only apt complexes, but by the time I graduated, they all had to allow children. There must be some kind of exception for senior centers though, there are several of them around here.
actually, you're right. years ago you could refuse to rent to someone with pets or kids. and even though i lived in an adults-only community, there was probably no clause in the lease that prohibited children. there were six different 11-story buildings in the complex and children may have lived in a different area. or, because of its proximity to downtown, people with children may have just preferred live somewhere else. i think legally, the only age-limit allowed on rentals is
a senior community. some people have complained, but i also live in a smoke-free building. it's legal to prohibit cigarette smoke in colorado even in private dwellings since 2006. however, since amendment 64 passed, i often smell a different kind of smoke in the elevators.
it's illegal to discriminate, but landlords often find other reasons to discourage tenants they don't really want. a bad credit check is one of those ways.
i agree, mutilating animals for a lease stipulation is abominable.