I read the really funny story about 30-40 years ago, probably around the 1970's to 1980's. It was a short that tells how 3 races (one human, one insect-like and one ???) land together on a new planet with a species that is really annoyed that the strangers just sit on the ledge of the door of the spaceship instead of attacking them.
Eventually they take the human and imprison him. While he's there, the insect flies inside to work out the plan to get this planet to cooperate with them.
This doesn't match some of the plot points you describe but I'll mention it because it's a close match in some ways and I wonder if it's possible you may have conflated two stories over the decades.
Anyhow, your description immediately reminded me of Diabologic by Eric Frank Russell. This was written in 1955, but I remember first reading it in the 70s. Wayne Hillder is a scout looking for new worlds and finds the first planet with a spacefaring race:
As he gazed down through his tiny control-cabin's armor-glass, he knew that this was to be contact with a vengeance.
During long, long centuries of human expansion, more than seven hundred inhabitable worlds had been found, charted, explored and, in some cases, exploited. All contained life. A minority held intelligent life. But up to this moment nobody had found one other lifeform sufficiently advanced to cavort among the stars.
Humans have devised a psychological technique for dealing with first contacts, hence the title, and his first action is to sit on the door ledge just as you describe:
Switching it off, he opened the inner and outer air-lock doors, sat in the rim with his feet dangling eighty yards above ground level. From this vantage-point he calmly surveyed the mob, his expression that of one who can spit but not be spat upon. The sixth diabological law states that the higher, the fewer. Proof: the sea gull's tactical advantage over man.
Being intelligent, those placed by unfortunate circumstances eighty yards deeper in the gravitational field soon appreciated their state of vertical disadvantage. Short of toppling the ship or climbing a polished surface, they were impotent to get at him. Not that any wanted to in any inimical way. But desire grows strongest when there is the least possibility of satisfaction. So they wanted him down there, face to face, merely because he was out of reach. To make matters worse, he turned sidewise and lay within the rim, one leg hitched up and hands linked around the knee, then continued looking at them in obvious comfort.
Wayne is captured but continues to use diabologic techniques:
The stranger dismounted and promptly got tossed into the clink. The result of that was odd, too. He should have resented incarceration, seeing that nobody had yet explained the purpose of it. But he didn't. Treating the well-clothed bed in his cell as if it were a luxury provided as recognition of his rights, he sprawled on it full length, boots and all, gave a sigh of deep satisfaction and went to sleep. His watch hung close by his ear and compensated for the constant ticking of the auto-pilot, without which slumber in space was never complete.
He is interrogated and eventually ends up talking to an alien called Morfada. By this time he has so thoroughly confused the alien race that:
"Somebody has to make a decision, seeing that the top brass is no longer capable of it. I am going to suggest that they set you free with our best wishes and assurances of friendship."
"Think they'll take any notice?"
"You know quite well they will. You've been counting on it all along." Mordafa eyed him shrewdly. "They'll grab at the advice to restore their self-esteem. If it works, they'll take the credit. If it doesn't, I'll get the blame." He brooded a few seconds, asked with open curiosity, "Do you find it the same elsewhere, among other peoples?"
"Exactly the same," Hillder assured him. "And there is always a Mordafa to settle the issue in the same way. Power and scapegoats go together like husband and wife.
I think you are looking for Retief's War by Keith Laumer. which was written in the 1960's. It was a kind of satire of the end of WWII and the begining of the Cold War.
As i recall, Retief and an insect aide land on a planet of robots who can only relate to each other through violence. Retief has to put on a robot costume and fight several of them to get them to agree to talk. The insect aide sneaks out because he painted his exoskeleton silver or gray, and the locals thought he was just another robot because each looks totally unique.
