Texas makes it a crime to use force to resist arrest, even when the arrest is unlawful, with an exception for when more force is being used than necessary to make the arrest. Considering Tom Jefferson's ribs were broken, putting him out of work, there's a pretty good argument that more force was used than necessary in his case.
http://www.statutes.legis.state.tx.us/Docs/PE/htm/PE.9.htm Scroll down to Subchapter C
(b) The use of force against another is not justified:
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(2) to resist an arrest or search that the actor knows is being made by a peace officer, or by a person acting in a peace officer's presence and at his direction, even though the arrest or search is unlawful, unless the resistance is justified under Subsection (c);
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(c) The use of force to resist an arrest or search is justified:
(1) if, before the actor offers any resistance, the peace officer (or person acting at his direction) uses or attempts to use greater force than necessary to make the arrest or search; and
(2) when and to the degree the actor reasonably believes the force is immediately necessary to protect himself against the peace officer's (or other person's) use or attempted use of greater force than necessary.
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Sec. 9.33. DEFENSE OF THIRD PERSON. A person is justified in using force or deadly force against another to protect a third person if:
(1) under the circumstances as the actor reasonably believes them to be, the actor would be justified under Section 9.31 or 9.32 in using force or deadly force to protect himself against the unlawful force or unlawful deadly force he reasonably believes to be threatening the third person he seeks to protect; and
(2) the actor reasonably believes that his intervention is immediately necessary to protect the third person.
Regardless of whether or not it's "technically legal", resisting arrest may not be conducive to Texas passing less restrictive open carry laws, and at least in this case justice can still be pursued for those falsely arrested and injured. That doesn't mean I'm ok with citizens being abused just so they can be held up on a pedestal for political reasons, don't get that impression...