This happens in every match at least 3-5 times. Ignore the gamesmanship or yell back. My call, not the players!
A solo referee starts to sell the offside call before the match begins. During the meet and greet with the coaches, and again in meeting with the captains, you remind them that you'll do your best on the offside call without ARs. When I have to call solo an offside infringement that someone doesn't like, I usually can get away with - - my assistant referee probably let me down on that one. My experience is that there is nothing you can say or do when the close, but not offside call, results in a goal. Just recognize that someone will be upset, and get the game restarted as soon as possible. They know that 3 referees are better for offside decisions than 2, and 2 are better than 1.
To the offside player: "Ah come on that was my one easy call for the match, you'll have to try harder next time lads"
1) Blow your whistle and point to AR 2) Follow up by a quick *tweet, tweet* and calm down gesture. 3) Loudly tell defenders. "I got this. If you scream and yell it makes it harder to make the calls seem like mine. Chill. Please and thank you." 4) Collina stare coach until he gets the message. 5) Thumbs up to AR. 6) Restart.