also, seventh, you appear to be a bit selfish, acting like humans are the big smartasses of the universe and shouldn't care about any life progressing forward at all :V
The snake population isn't rampant enough to cause extinction via competition of species.
Feeding it because you need to feed it is different from feeding it for entertainment
What you fail to realize is that there is almost absolutely no difference between them if it's accomplishing the goal of feeding it.
It's like this, you go to McDonalds and you buy a hamburger. You eat it incredibly angrily and shout a bunch of racial slurs against cows while doing so. Therefore it is animal cruelty because you aren't eating the hamburger because you're hungry, you're doing it because you hate animals.