OK State Rep. Justin Humphrey, the lawmaker who drafted up the Bigfoot bill, tells TMZ ... he's getting tons of backlash from believers and non-believers alike.

Rep. Humphrey says he's been flooded with calls, emails and Facebook notifications from Bigfoot deniers, calling him an "idiot" and cussing him out. He says folks are telling him they'll NEVER vote for him and they're gonna make sure he loses his next election.

The Bigfoot non-believer beef -- the proposed bill is a big waste of time because sasquatches don't exist and there are more important things for lawmakers to worry about.

Rep. Humphrey tells us Bigfoot believers are annoyed with him too, but they're laying off the verbal attacks and keeping it civil. He says these folks don't want anyone disturbing Bigfoot or the forests where he supposedly lives.

BTW ...the lawmaker says the bill's not calling for Bigfoot's death ... rather, it's asking for someone to catch the creature, and he's hoping for a $25,000 reward for the first trapper.

Oklahoma's infamous for its Bigfoot sightings, particularly in the southeastern and southern parts of the state, which Humphrey reps ... but he tells us he's seen no evidence Bigfoot exists, aside from some mysterious photos.

Rep. Humphrey says the point of his bill is to generate revenue with tourism, hunting licenses and tags, encouraging folks to enjoy the outdoors after spending more time inside due to the pandemic. But, it seems like most folks didn't read between the lines.