He clearly broke the law: 18 U.S. Code § 879 - Threats against former Presidents and/or their family members. No question he was telling people to kill Clinton to protect their gun rights.
(a) Whoever knowingly and willfully threatens to kill, kidnap, or inflict bodily harm upon?
(1) a former President or a member of the immediate family of a former President;
(2) a member of the immediate family of the President, the President-elect, the Vice President, or the Vice President-elect;
(3) a major candidate for the office of President or Vice President, or a member of the immediate family of such candidate; or
(4) a person protected by the Secret Service under section 3056(a)(6);
shall be fined under this title or imprisoned not more than 5 years, or both.
(b) As used in this section?
(1) the term ?immediate family? means?
(A) with respect to subsection (a)(1) of this section, the wife of a former President during his lifetime, the widow of a former President until her death or remarriage, and minor children of a former President until they reach sixteen years of age; and
(B) with respect to subsection (a)(2) and (a)(3) of this section, a person to whom the President, President-elect, Vice President, Vice President-elect, or major candidate for the office of President or Vice President?
(i) is related by blood, marriage, or adoption; or
(ii) stands in loco parentis;
(2) the term ?major candidate for the office of President or Vice President? means a candidate referred to in subsection (a)(7) of section 3056 of this title; and
(3) the terms ?President-elect? and ?Vice President-elect? have the meanings given those terms in section 871(b) of this title.