Simply more anti American revisionism.
The Americans can do no reight for any reason.
What doees John Kerry and company run nick?
Sometimes telling the truth IS anti-American revisionism, but it's still the truth.
Yes, a major issue that led to the War for Texas Independence was slavery -- the Mexican government outlawed it, the American settlers (and some of the Americans living in Mexico were actually ILLEGAL IMMIGRANTS!) wanted it. Travis spent some time in jail for leading a group against Mexican authorities, protesting the anti-slavery laws. What the movie (haven't seen the Nick spot, so I can't speak to that) glossed over was that a major component of the Texicans' issue with the Mexican government was that government's (by then, the dictator Santa Ana's) decision to combine provinces and leave the Texas area without political representation; a similar issue to that which inspired the American Revolutionary War. So patriots are patriots, and some of the same ideals that led to America, led to Texas.
As far as Crockett goes, I thought the movie was a nice balance between the Pena diary and the early movies. When it comes to Crockett being a drifter, you gotta admit he DID roam a bit as a younger man, and his defeat in the election for congress (as well as his p-ssing off Jackson over the Indian removal issue) probably made him realize he would do well to find opportunity elsewhere. So we now have his famous, "You can go to hell, and I'll go to Texas," line (where DID these guys come up with such great one-liners without movies to provide them?).
Crockett's thoughts about going over the wall? A great bit of humanity. There are a LOT of people who would like to escape some unpleasant situation, but instead are everyday heroes who plunge ahead, and sometimes the reason is because someone who looks up to them is watching. Crockett voicing what a lot of people would be thinking brings him down off his pedestal a little, that's true, but in my mind it makes him much more real. And when you're trying to explain something like the Alamo to a bunch of 8th graders these days, real works a lot better than fairy tale.
I suppose you'd really have an issue with the movie if it went into how the American government was secretly providing Texican filibusters with guns and money to stir up trouble in the Texas area before the war started.