Dennis Rodman -- 'Bruce Jenner Would've Had Ass Handed To Him ... If He Did This In '90s'

Bruce Jenner would have had his "ass handed to him" if he came out as a transgender woman back in the '90s ... so says someone who spent a lot of time in women's clothing, Dennis Rodman.

The Worm just called in to "TMZ Hollywood Sports" and says he's extremely proud of the way people are accepting Caitlyn ... and says society has come a LOOONG way in just a few short decades.

In fact, Rodman says he specifically remembers spending HOURS trying to talk Sports Illustrated into letting him pose on the cover in women's clothing back in 1995.

Now, Dennis says he thinks Jenner is breaking down some huge barriers for the LGBTQ community -- telling us, "A lot of athletes will come out now and say they're gay. Watch."

And with Caitlyn saying she's still trying to figure out her sexual preference, Rodman has a message for the 65-year-old -- "If you wanna go on a date with me brotha, let me know."