Don’t worry about Piers. He’s still a rabid gun-hater. He had that idiot sportscaster Bob Costas rant his hatred of guns all over morgan’s show. Stick to jock-sniffing, you sissy.
People have made up a lot of explanations for both spellings, but I believe “toe the line” is the correct usage. FR is the only place I have ever seen anybody use “tow the line”.