You misunderstand, they didn’t call for killing the President, they called for killing the private citizen, potentially after he’s been stripped of all protections through impeachment.
If he is impeached and the Senate votes to convict, then he will lose benefits. At the moment, however, it is believed that the Secret Service detail will remain in place regardless.
0: https://www.congress.gov/bill/112th-congress/house-bill/6620