A former 'Bachelorette' producer is calling BS on the idea that ABC was blindsided by Taylor Frankie Paul ’s physical violence allegations involving her ex, Dakota Mortensen ... telling us there’s just no way that slipped through the cracks. We spoke with Michael Carroll on "TMZ Live" Wednesday ... and he says back in his day, casting was unbelievably strict -- with deep background, medical, and psychological checks on every contestant ... adding that anyone with charges like that against her