I would like to buy a 2 horse BP trailer one day but my #1 concern is having something to pull it with. 

Hubby has a 2005 Dodge Dakota Laramie 4x4 Club Cab with a 4.7L V8.  We rented a 2 horse trailer one time & they didn't want to rent us the trailer because our truck wasn't "big enough".  (They did in the end because we were only going 5 miles down the road).

I think the towing capacity is 7700#.  Can it tow a horse trailer safely? 

Yes, properly set up with a WDH and brake controller it will be fine.  There is much confusion and trepidation when it comes to towing with modern mid size vehicles......most (IMO) of it coming from "older, experienced" drivers that dont have current experience with the highly capable modern vehicles.  I towed for several years with the Trailblazer and 2h in sig, it towed, handled and stopped fine........so well in fact that I delayed the intended purchase of the 3/4 ton now in sig.  You will hear horror stories of the "tail wagging the dog", and "you wont have enough brakes" (which is complete BS) when using smaller trucks........but for every one of those, I have had similar close calls over the years in larger trucks, generally the truck is not the problem.  All that being said, YOU may end up not liking how the Dakota handles the load, but to answer your question.....it can be done safely.

Well, you already did it according to your statement, how did the truck react when you towed the trailer?...

Just don't try hauling a team of drafts...

If you have 7700# towing capacity, then subtract the weight of driver, passenger and anything placed in the truck...

Then just start subtracting all the weights you know...

horses, tack, et cetera that will be in the trailer...

then figure out the weight of the trailer you want

and if the numbers haven't gone negative...you should be okay...

Ooops... failed to mention that we never got the horse on the trailer.  She absolutely refused to get on it & I had taken the day off of work & everything and we got absolutely nowhere.

So hubby just towed the empty trailer about 5 miles to the rental place & back.... we never got to see how it felt with the horses.

Thanks for the help everyone!