Fixed links from above:
I don’t think that you have ever seen an episode of That Girl! as Bessell was a much larger man than the person who is shown in the picture.
Here’s a video of Bessell.
Clearly the seated person is NOT him.
Looks much older then Bessell to me, with thinner hair.
Not Mulhare.
He was a much taller man (6’2”)
The man seated is clearly 5’8” to 5’ 10” at the tallest.
Yeah, don’t know what I was thinking when I suggested Klugman - his hair wasn’t wavy. 
Seriously though, I thought the camera may have caught him in a transition of expressions similar to what another poster described, and so didn’t look like we normally think of him. Subsequent viewings on Google however have disabused me of that notion.
Could be producer Danny Arnold, except he does not show an imdb listing for that show under self – and the face looks familiar, he looks to me like an American comedian.
Robert Young’s height is listed at 6.0’. The man in question does not appear to be shorter than Young.
I feel sorry for those few who didn’t have a variety show back then.
But I was hinting that Michael Constantine was the guy. He has the same smile and won an Emmy that year so he would have belonged on that stage.
Which one is he, the left or the right? 
It’s Mel Ferrer. He was “a star” when this photo was taken, whereas Peter Mark Richman (who does have a similar look) was not.
Some pics can be seen at:
I repeat that this photo may not be from 1971, but rather from the November 11, 1970 broadcast, when according to TV listings for that date, every single person in the picture was on the Tonight Show (due to their having won an award at the Photoplay Awards).
It seems unlikely that the same exact grouping showed up a year later for a reunion because they all won Emmys.
Michael Constantine wouldn’t be a bad guess, except I think his hair is so dark that even the lights wouldn’t turn it that shade of golden brown. Also, his eyebrows are… a lot more prominent, shall we say. 
I’m going to take back Mel Ferrer and nominate Graham Kerr.
According this link guests that night were:
Mystery man doesn’t look like John Wayne, so maybe it’s Bette Davis as a cross dresser.
Not even close, I remember Graham Kerr from that time period, that is not him.
Yipe, I think Graham Kerr is even less likely than Mel Ferrer. Kerr’s hair was a) super-straight and b) super-dark at that time. Also he looks nothing like this guy. Other than that…
Holy shitsnacks, I posted that on the last page, along with an actual newspaper TV listing. Am I invisible?
Another vote for Bessell. There are other pix on the Interwebz of him and he’s a match all the way.
I’ve been having that invisibility problem lately too.
Sorry, but Kerr is at LEAST 6’3” or 6’4”.
The man seated is less than 6 foot tall.
Constantine in the 1960s.
Lower RHS.
A little too “Greek” to be the man seated