John Malone's claws came out first in the courtroom catfight of the moguls that got underway Monday at the Delaware Chancery Court.

Malone, chairman of Liberty Media, got a few digs in about Barry Diller's prowess as a chief executive at IAC/InterActive Corp., observing that IAC's stock price has been "extremely volatile"  since the company "went into Internet space."

He added, archly, that IAC stock has been "a very poor performer" compared to stock indexes, a phenomenon he called the "Barry discount" in a Wall Street Journal story last October.

Diller, meanwhile, has been "extremely well compensated," and "developed some pretty aggressive approaches to personal use of corporate aircraft. Mr. Diller made it a fine art."

Corporate jets figure prominently in this slugfest: The two ran into each other at the Teterboro, New Jersey, airport on Jan. 16, just after a tense IAC board meeting that Malone—called Dr. Malone at this trial—spelled the end of their 13-year partnership.

At the airport, Malone told Diller, "I know you want to run your own show," and suggested negotiating an amicable divorce. To which Diller responded, "Amen," according to Malone's testimony today.

The parting, alas, has been anything but amicable.

Diller and Malone are fighting over control of IAC, a $5 billion company that Diller built with Malone's backing. The company includes Ask.com, Ticketmaster, and the HSN home-shopping network.

Diller wants to divide the company into five pieces, all of which would no longer carry a dual-class stock structure. Malone's Liberty Media, which owns 30 percent of IAC's equity but nearly 62 percent of its voting stock, opposes the deal.

But Malone gave Diller a proxy to vote Liberty's shares as he saw fit. Or did he?