Columbo was calm at the entrapment of Vivian Dimitri despite trying to murder Mrs. Columbo and Columbo himself.
Compared to the hounding of Miss Hudson in Prescription Murder and the judgemental speech in Ranson for a Dead Man, the arrogance and hardness of Columbo seems more geared to the killers' reactions in later episodes than to a simple evolutionary explanation.

I have characterized him in the past as changing from "humble and mildly eccentric" to "arrogant and goofy". When he yells at people like Joan Hudson and Dr Barry Mayfield, I don't view that as "arrogance", I would rather characterize it as anger or frustration. When I say he became arrogant later on, I am referring to this extremely patronizing tone he develops, and which he has almost throughout the entire program such as "Make Me a Perfect Murder". It is like he is saying "I am the great Lt Columbo and I am going to cut you to pieces". In earlier ones, he seems less sure of himself and he shows greater "respect" (as it were) for his opponent. It is that persona that I like the most. I also like it on the rare occasions he gets angry because it makes him more human.

In addition, making Columbo a gourmet in "Murder Under Glass" is TOTALLY out of character with the chili and hot-dog loving Lieutenant we grew to love in the earlier programs.

I do not reject, however, all the episodes from Seasons 6 and 7...."Fade Into Murder" and "The Conspirators" are quite good and Columbo reverts to being humble in them.

You beat me to it YM. I too, don't see Columbo's hounding of what's-her-name in "Prescription Murder" as arrogance. She was suspected of murder. Guess it depends on your definnition of arrogance. I don't see his outbursts in "Stich of Crime" or "Exercise in Fatality" as arrogant either.
I liked his "don't count on it ma'am" line in "Try and Catch Me". I saw it as a kind of gentle warning, even an apology that he had to do his job.

I was interested to hear how he stopped referring to his wife and started caling her Mrs Columbo. That is a subtle change and reminded me how much better it was when he did call her his wife.

Did Columbo get more arrogant as the series progressed? It's a good question. Perhaps, in accentuating the kooky side to his nature, in being a slightly more lighthearted (even at times whimsical)Columbo, he doesn't seem as earnest, as genuine, and appears slightly more arrogant, more self assured.
He bungs it on with his forgetfulness and whole schtick but now it seems even more contrived.

I guess he seemed to be more making fun of his suspects in the newer eps, patronising them more often with a wry smile and a wink to the audience that to me suggested a more arrogant Columbo.

I have no idea what Chief Clifford is referring to. I don't see arrogance to anywhere near the degree he described at all.

I actually like the scene with Kate Hudson in Prescription Murder. Miss Hudson is young, naive, and is being used by Dr. Fleming, but she also participated in a murder, and is covering for it. I think Columbo's outburst is justified and is an attempt to break the spell Dr. Fleming has over her; an attempt to appeal to her conscience, and the line "that woman would be alive if it weren't for you" is true, so I would say it's very justified. It's also a piece of superb acting which is enjoyable to watch!