There's a lot of things besides nudity that can render an image inappropriate for use in a conference presentation, and judging from the description in the linked article (There was one image of a pig indulging in sexual activity with a goose...), I don't think it's unreasonable to expect people to be offended.
Sure; but if you are presenting in public, it isn't your own 'offended' threshold that should be operative, it is that of your audience. And, even there, you probably don't want to shoot for the middle of the pack there-- offending, say, half of your audience wouldn't be much of a success in most contexts. So, while you might not want to scrub down your presentation to a point where no one is offended, you still probably want to stay away from sexual images involving farm animals. Just sayin'.