zlacker

Don't take legal advice from Hacker News, obviously :-)

In Texas[0]:

  (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.

Elsewhere:

  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.

Assuming you survive the encounter, it is possible you could prevail on your day in court.

[0] https://statutes.capitol.texas.gov/Docs/PE/htm/PE.9.htm#C

replies(1): >>brendo+Wi