Firstly, please ask your friend to show a published court opinion or a statute that states that the police have an affirmative duty to respond to a 911 call.
Secondly, the police in your linked video did not have reasonable suspicion of a crime, making the detention unconstitutional and anything else found after that would be a fruit of the poisoned tree. Thompson v Oklahoma:
Thirdly, OK does not have a Stop & ID statute.
Fourth, the US Supreme Court declined to make a 'firearms exception' To the 4th Amendment in JL v. Florida.
Finally, your LEO's theory that he can charge someone with obstruction for taking the 5th is just plain bullsh1t and attempts to do an end run around the 5th and convert the assertion of a right into a crime. Case law is clear on this matter:
"The assertion of federal rights, when plainly and reasonably made, is not to be defeated under the name of local practice." Davis v. Wechsler, 263 US 22, at 24
"Where rights secured by the Constitution are involved, there can be no rule making or legislation which would abrogate them."Miranda v. Arizona, 384 US 436, 491.
"The claim and exercise of a constitutional right cannot be converted into a crime." Miller v. US, 230 F 486, at 489.
There can be no sanction or penalty imposed upon one because of this exercise of constitutional rights." Sherer v. Cullen, 481 F 946