the.com/line of fire

means The path a projectile or attack is expected to travel, and by extension any position of exposure to danger, criticism, or blame.

from A literal military phrase from gunnery and artillery — the actual trajectory a shot would follow from muzzle to target, something soldiers were drilled to track so as not to stand in it. By the 19th century it had already started drifting into figurative use, for anyone caught in the path of harm, and later for anyone catching blame, criticism, or scrutiny not meant for them — the shift from bullets to insults being, etymologically, a pretty small step.