I think one of the biggest problems with a blanket "no offensive content" policy is that it is, as we have discovered, a very personal issue.
What I find offensive may not offend you, and what offends you might not offend me.
Also, making policies like this are generally just going to create argument as people disagree on the offense level of one question over another, moreso as motive is perceived or assumed.
At the end of the day, we are all here because we ostensibly care about pets, and this is why we have a site dealing with issues relating to the care and keeping of them. There are going to be times where we need to tackle sensitive content (sexual/mating matters, death and illness, etc), and we need to all be prepared and open to those possibilities, as they are natural questions that can come up as part of owning pets.
While people may have issues with, say, sexual content, for a variety of reasons (personal, moral, not safe for work, etc), I think that we can work to make an environment where people can ask reasonable questions on those sorts of topics without it becoming a giant NSFW-fest where people are getting uncomfortable left and right.
We want to become a good resource for pets and pet-related issues, which means that sometimes, questions are going to come up about things people need to deal with that might not be entirely comfortable for others. Remember, you always have the ability to ignore tags and the like to customize your experience.
In the end, I think these things need to be judged case by case on their merit as an actual pet-related question.