Paraphrasing Boris Becker once after he lost at Wimbledon, "Nobody died and we aren't at war."
Both sides should show consideration to the other. Hawkeye provides for great fairness. Professional athletes should be able to be professional and their entourages should follow suit. If the players aren't actually fighting then why would the friends?
If a fight actually did break out in the friends box it would probably be Great for Tennis as entertainment.
Best experience I ever had playing a tennis match was when my opponent's parents only clapped for my good shots, while I got tuned. Told me alot about my opponent and his parents.