Couple things to keep in mind here.
First thing is that filters won't stop paintballs, and will in fact make a lens hit worse. A filter is simply a ~1mm pane of glass and offers no impact protection of any value. When one breaks, the shards of glass get forced against the lens and will almost certainly scratch it. Clean-up becomes an extremely delicate operation, as you've now got paint laden with glass all over your lens.
Why do so many still use filters then? Shooting paintball is dirty business. Dust, dirt, paint, rain and god knows what else will find their way onto the lens. Rather than grind these things into the lens when you go to clean it, you have a $50 filter that can take the hit on those repeated cleanings.
Second is that your camera body is tougher than you think. The shell will not crack if it gets hit. The only things to be wary of are liquid intrusion and direct hits on displays. In your case, the Rebel only has a rear LCD, and the odds of that being exposed to a hit are low. Liquid paint intrusion is a concern around controls and the lens mount. The force of a hit can drive paint into the body.
Solutions here vary considerably. Some folks fashion neoprene covers, others use plastic bags or rain covers. A few use nothing, but are usually using weather sealed bodies. Camera Armor sometimes comes up here, but doesn't really offer complete protection against liquid paint.
I like to use a Kata rain cover with a small modification. I have a page detailing how it works here
. The cover essentially forms a little bubble protecting the camera and my hands. This is a field tested solution that I've been using for years.
The most important thing you can do, though, is avoid situations that send paint your way. If you pay attention to the game, you can stay ahead of the action and avoid the lanes of fire.