This kind of comment or indeed any kind of snark at one's horse's best use requires the judicial response of "Well, bless your heart" (tone of voice should imply, my goodness, how amazing that someone as obviously developmentally delayed as you are can actually speak, although of course it is too much to expect that you would ever make sense...)
The public perception of "trail horse" tends to encompass all of the following things:
- too lame to jump
- too backsore to do dressage
- not pretty enough to compete at anything
- too ugly of a mover to ever make it in the show ring
- too dumb to learn anything more advanced
Note all of the free horses with a line like "may be okay for light trails" in the ad. Translation: really, really lame. May walk around the paddock sound on a good day with some bute and corrective shoeing.
That's why the OP was insulted. I understand that if you do "serious" trails it takes a level of skill and athleticism that is impressive, but many people perceive "just a trail horse" as something that can maybe, on a good day, walk and trot down a level trail for an hour without going lame.
Actually...I would have taken it as a compliment too (and if the person didn't mean it that way, you could always disarm them: "I know - he is so solid and safe and sane on trails...that's the TB smarts coming through! They know how to take care of you in any situation!").
My TB is not spooky, loves going places and seeing things. I don't ask for contact when we hack out because he's looking at stuff, not spooky looking, just curious (and the geek in me thinks that's okay).
That being said - he is a great PASTURE hacking horse. He doesn't like to cross water (you have to show him it's not deep first), he doesn't like plants and burrs and stuff getting on him (to say the least), he doesn't like bugs at all. This is not the horse that would enjoy a 3-5 hour trail ride up and down a wooded mountainside. And there's a lot to be said for a horse that does take that in stride.
The flip side being, of course, that that uber sensitivity makes a terrific dressage horse and a wonderful teacher.