That's untrue about males. They're very easy to introduce -- it's all a matter of personality. Usually when male pigs "don't get along" or "don't like other males" it's because introductions are done improperly or they're in tiny pet store cages.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry