You see all good and all evil! You must be a god! Therefore I'll press the button since you seem to think so, and I know you'll have mercy on my soul.
About purpose, people seem to have their own purpose, (only personal not absolute) but do you think a paramecium has that same awareness of self worth? Even if not, that doesn't mean they don't have a right to live.
Nature is very competitive for survival, but humanity clearly oversteps this boundary. We kill other life forms and sometimes entire species for convenience, luxury, etc. Humans are the only species not "playing fair" so they should be ejected from the game. The button needs to be pushed.
I would spraypaint the button green and draw a dollar sign on it, and tell some sucker nearby that it's the free money button (just for liability purposes, I won't be the one to push it).