Modern Family Star Accused of Starting Fight At Dodgers Game

The Cardinals fan in question -- a guy named Michael Gallagher -- says the drama began when he heckled Matt Kemp for grounding out at the bottom of the 8th.

Gallagher says he yelled, "Hey Kemp, 0 for 4, nice job!" ... and Kemp rolled his eyes, laughing it off.

According to Gallagher, Stonestreet was sitting next to him and yelled back, "Matt Kemp should've come over and punched you in the face."

Gallagher claims Stonestreet then approached a security guard and said something to the effect of ... "Someone needs to kick this guy's ass."

Gallagher tells us, Stonestreet continued to yell insults at him and his friend, such as "Nice v-neck" -- and finally his friend snapped, yelling back, "Well you're a fat ass!"

According to Gallagher, that's when things got out of hand -- and the actor came over to exchange words up close.

Security quickly intervened and escorted everyone up to the main concourse -- at which point Gallagher says Stonestreet whipped out the infamous line ... "Don't you know who I am?"