All animals are not the same.
In Torah/ Talmud it explains that domestic livestock (such as sheep and cattle) can be slaughtered calmly and humanely without high levels of panic and terror. This is the reason such animals are kosher (nothing to do with cleanliness).
Other animals like dogs, cats, apes, camels, horses and whales have an accute sense of death and they suffer great trauma, terror and anguish no matter how you try to slaughter them. This is why those animals are un-kosher.
Although gentiles are not required to keep kosher, I believe that the kosher guidelines are worth following for ethical reasons.
Scientists have tought American Sign Language to Gorillas and found that they are capable of conversing with us like 6 year old human children. Whales have a sonar vocabulary as comprehensive as our own and have very close familial relationships and bonds. How can we eat such creatures in good conscience?
Sheep & cattle? No problem. All others.....NO!