Morality is bendable, just because some people say it's wrong or weird.
Where does morality come from?
Why should it be limited to two? And if the animal's not injured or discomfited in any way, why is bestiality wrong?
You sure opened a can of worms there. We risk delving into theology, and education, and law codes, and a lot of other seemingly unrelated topics. But let us take this down to the most pragmatic level, just learning from experience. What works, and what doesn't? Should we confine ourselves to what works, or do we experiment continually? Continual experimentation generally results in something like the Darwinian competition, resulting in removing the overly adventurous from the gene pool. On the other hand, confining oneself to only known and proven ways is a sure sign of stagnation, and eventually some rather close inbreeding. Neither position would be particularly "moral" in that a bad outcome occurs with either course, both of which may be considered to be "extreme". But somewhere in that gray area between too much innovation and too little, there is a range of acceptable behavior that ought to be emulated and encouraged. Some things are not done, because of the overall hurtful effects that greatly outweigh any potential benefits. Some things are so overwhelming useful and the outcomes so brilliantly admirable that great effort should be made to repeat the behavior. And note that I never once mentioned God, or mother, or policemen. Doing the right thing, even when nobody is looking, is the definition of personal morality. Also defines character.