When did it become cool to disrespect the national anthem?

Short answer: It's not.

I used to live in a nation where it was verboten to disrespect the national anthem and the flag. Long ago, the Left made desecration of the flag an acceptable form of political "speech" and the Supreme Court agreed.  We acceded to this, because it was rare and flag burners were obviously radicals who we knew hated the country.  When Smith and Carlos raised the Black Power salute at the '68 Olympics, they were roundly criticized, but it was understandable in the context of the times.  It was wrong then, and remains wrong today.

Colin Kaepernick thought he'd give himself some relevance by latching on to the morally bankrupt and dubious BLM agenda by taking a knee during the national anthem last year.  He's really the symptom, though, of something that has been happening really since the '60s, the inability, or unwillingness of people to appreciate, that by the miracle of the place of their birth, they get to live in the greatest, freest, most tolerant and diverse country on the planet, where people, even today, can rise from poverty to be a Supreme Court jurist, or run a huge fast food chain, coach a Super Bowl winning team, or even be President.

We need fewer Colin Kaepernicks and more Alejandro Villanuevas.

Now, here are some things I don't need.

I have no need of people disrespecting the country that is a beacon of freedom to the world, that has enshrined individual rights in its Constitution, and that has only asked in fighting foreign wars for a place to bury its dead.

I have no need of people dishonoring the men who fought to secure that freedom and the men who wrote those documents, who did so at great peril.  If we had lost, every one of those men who signed the Declaration of Independence would have been tried as a traitor to Britain (they were) and likely executed.

I have no need of people who won't acknowledge that hundreds of thousands of men died in a bloody civil war to free slaves and reunite the union and ensure the promise of the Declaration.

I have no need of those who ignore that these men's sons and grandson's fought in two world wars, in one final act saving the world from the scourge of the Nazis.

I have no need of those who find it acceptable to disgrace the men and women who served under the flag when the government wasn't allowing them to win in Vietnam, and conversely, when the government did provide the resources to face down the Soviets and stick the failed ideology of communism into the ash heap of History where it belongs.

I'm not a fan of compulsory military service, but, I think there's merit to the argument.

Why?

As the percentage of the populace who serves in the military continues to decrease, we find ourselves as a society increasingly disconnected from the personal sacrifices faced every day by men and women who serve, willingly, in dangerous places like Kabul, Mosul, Syria; at bases in far removed from their families like Djibouti, Guam, Diego Garcia, Incirlik, and on ships at sea for months at a time.

For parts of the country (I'm looking at YOU, Northeast and California), you're half as likely to run into someone who served as in the Sunbelt.  It's easy for rich, entitled brats to enjoy the blessings of liberty when they're largely being secured by young men and women from the places they detest.

Because we no longer enjoy the shared experience that every family could sit down for Thanksgiving Dinner and pray for at least one family member who was serving, or had served, we have fewer and fewer collective connections to our men and women who protect us, at great personal sacrifice, every day.

When BLM,  millionaire pro athletes, Hollywood Liberals, or NYC-DC axis "journalists" preen about anthem protests being about racism, or police brutality, or about the plight of minorities in this country, forgive me if I barf and say "Screw you."  The anthem is about these men and women who served. It's about the men who gave us this Republic.  It's about freedom.

It is one of the last of those shared experiences that ties us ALL to those who nobly made this country the last, best hope of earth.  It is why removing our hats, facing the flag, and placing our hand over our heart for 3 minutes at some sporting event is so important. When you abstain, you dishonor these men and women. Period.