A hostile witness on the premiere of ABC's new "Viewpoint" program complains of TV, "The problem with television is you have to say it all in 20 seconds." Cut! He's off the air in less than 20 seconds himself.

Be that as it is, "Viewpoint," getting a trial outing at 10 tonight on Channel 7, constitutes refreshing and remedial network programming. A million sentences could begin with the phrase "the problem with television," but few of these problems are ever discussed on television itself. This program, hosted by Ted Koppel and produced largely by the agile "Nightline" staff, may not be a quantum leap, but it is at least a hop in the right direction.

And it's tidily appropriate that the program is airing on the network whose news department is the most frequently criticized. Much of the first hour is given over to stories from previous ABC News broadcasts that evoked complaints, rncor or outright denunciation. In this regard, the program serves as a kind of housekeeping for the network; in one segment, it attempts to polish off the longstanding grievance against ABC News held by Kaiser Aluminum over a "20/20" report on allegedly hazardous aluminum wiring.

Kaiser, whose officials had declined to be interviewed for the report in the first place, demanded time to respond to Geraldo Rivera's piece after it aired on April 3, 1980. There was a lot of subsequent back-and-forth about when the response would air, if it would air at all and who would control it. Tonight on "Viewpoint" the Kaiser-produced rebuttal finally gets shown. It is unconvincing.

First, of course, ABC News uses this program as an excuse to air a condensed version of the Rivera attack all over again.

A little later, Koppel interviews Kaiser spokesman Steve Hutchcraft and reporter Rivera as the pair site side by side in a studio. To Koppel's credit, he seems as tough or tougher on River as on Hutchcraft. But he gets bogged down, as he sometimes does during his "Nightline" grillings, on one or two contested details, so that it remains for Hutchcraft, in the final moment, to bring up the wider issue that should have received more attention:

"What we have missed here tonight is to talk about the issue of trial by television . . . where the accuser is also the judge, the jury and the prosecutor, and the only way that the defense can make its point is through the voice of the accuser."

Rivera defends himself fairly well, except when he twice waves the pious banner of "the responsibility of responsible journalists." Senor J'accuse may not be the ideal flagbearer for that one.

Considred next on the program is the double-sided problem for minorities in television -- stereotype-enforcing coverage of them, and substandard hiring practices by networks and stations. There are about 20 black correspondents in network news now, it is pointed out, but these may amount to defensive camouflage; the fact is, says Lem Tucker of CBS News, there are no blacks in top decision-making roles at any of the network news divisions.

Max Robinson, the ABC anchorman whose speech charging "racism" at ABC was a klutzy misfire earlier this year, says there may be black faces on the air, but that "our perceptions and perspectives" are not solicited. Also interviewed in this segment are CBS News president Bill Leonard, ABC News president Roone Arledge and the increasingly capable WJLA-TV anchorwoman Renee Poussaint.

Segments on alleged anti-Arab bias in TV news and what it does to the sensibilities of Arab-Americans (nothing very traumatic, to judge from the interviews assembled), and on the stultifying subject of ERA, whose supportes and detractors have achieved true equality of abrasive speciousness, are low points from which the program never recovers, not even with a more animated ABC version of the old "Letters to CBS" show.

It doesn't take much cynicism to see the built-in image enhancement in projects like "Viewpoint." Yes, ABC is airing this first installment in prime time -- but it's July prime time, and in a slot opposite "Dallas," so ABC had no hope of being competitive in the period anyway. Viewers who watch all of "Viewpoint" will probably come away with the feeling that ABC News is terribly righteous and brave for the undertaking; the show is not philanthropy but, in part, shrewd public relations.

Nevertheless, there is much to find encouraging in the program. Television has been one of the subjects that television covers worst. Of ABC's effort at rectifying this, Koppel says, at the end of the hour, "It can't begin to satisfy everyone" but that the goal is to show "there are other viewpoints which deserve access to network television." A tiny step, maybe, but one well taken.