The simple answer to your question is YES. You can paint over Behr textured paint.
To kibosh the "why would you paint over paint": the Behr textured paint is less about being a "paint" in the traditional sense and more about a user-friendly, roll-on texture. True, you can get your Behr (and many other) textured ceiling paints tinted and shaken up like "regular" paint, however the color - especially if you're trying to achieve Ultra Pure White, won't happen without at least 1 coat over the textured layer.
On another note, you mention that you're using this in a bathroom prone to condensation. You may want to reconsider using a textured product altogether in high moisture areas as the nooks and crannies of the tex creates the perfect place for moisture to latch onto. It may take as much as a year or so, maybe less, but eventually textured ceilings exposed to daily steam/condensation/moisture WILL develop mildew in between the peaks and valleys of the tex paint; that leads to mold, and you'll be back doing the job again before you know it (like you are now).
Don't get me wrong, you can use the textured paint on your bathroom ceiling but if you wish to avoid the negative scenario above, you're going to have to use a higher-sheen top coat (satin finish at least, if not semi-gloss). These sheens are rarely ever used on ceilings as light bounces off them far more than flat and eggshell finishes, showing every little imperfection and looking a little... well... tacky. Satin finish is a middle-ground where you'll receive some benefit of a harder (shinier) paint without too much gloss.
I HIGHLY recommend the following:
1. The most obvious and extremely important - Allow the tex paint to completely cure (consult the back of the can and adjust as it directs for your climate/weather/etc) - If you fail this step, you might as well pack up and move. No not really.. but it is important ;)
2. Use Behr primer-sealer for satin, semi-gloss and gloss paints (or another brand if you prefer - just make sure you're using latex primer sealer if your tex paint is latex and vice-verse if your tex paint is oil based). Let cure.
3. Apply paint as advised above. Let cure.
3. Apply primer (and, once that's cured, paint) with a roller cover of at LEAST 1/2" nap
****You can only roll over an area ONCE when painting atop textured paint****
If you roll over a wet area (one you've just painted) as you would when painting a wall for instance, the wet primer/paint that you rolled on just before will have already stuck itself to your textured surface and will proceed to peel itself --and the tex right off along with it! I learned this the hard way ;) So, only one pass - no back and forth - no overlaps - just down one way ~ it's good practice to put a second top coat on after the first cures anyway ;)