Kat Von D to 'Good Day': I WARNED You!!

Kat Von D says she had a DAMN good reason for walking off "Good Day L.A." this morning -- telling TMZ, she made one reasonable request ... and producers repeatedly BLEW HER OFF.

Kat tells us, she agreed to answer a question about her breakup from Jesse James on one condition -- that the anchor didn't mention the split in his introduction.

But according to Kat, that request was IGNORED -- and as we previously reported, anchor Jeff Michael read out an introduction that highlighted Kat and Jesse's breakup.

Kat says she saw what was on the teleprompter long before Jeff read it -- and even pulled a producer aside to have someone change the script ... but nothing happened.

According to Kat, she "very politely" informed them ... if it wasn't changed, she wouldn't be able to go on. But no one changed squat, so Kat beat it.

Later, during the show, the executive producer went on the air -- explaining Kat's only prior request was not to bring up Sandra Bullock or Michelle McGee ... a request "Good Day" honored.