Both.
Being an arse, and becoming resistant to arseholes on the other side, can become an arms race in some sectors. It tends to break down after a while, when people on the supply end start “sacking” customers because they get enough business from the others that they can be choosy, then the cycle begins afresh.
Business
> often shouted and swore at suppliers to extract the best prices
Bully
Bullying. Full Stop.
This behavior gets people thrown out of restaurants and bars. If I ever catch someone treating one of my employees like that, and the employee is caught like a deer in the headlights because it is a big deal, I have absolutely no qualms stepping in and firing the client representative on the spot (clients can get back into our good graces by swapping representatives with apologies). I don't care how big the client is (I also perform receivables management to ensure no client is ever put into a position where they can threaten my book of business).
I've been told once by a purchasing manager after speaking with a client's company counsel that I drive a hard but fair bargain. Happy repeat clients to this day. We respected each other without anyone resorting to toddler-teenager tantrums during the negotiations.
When dealing with wait staff, hotel staff, valets, pool cleaners, all the way to CIO's and boards of directors, bullying is never acceptable. That you attempt to put a patina of respectability upon it by making it "just business" is also unacceptable. It's extremely disrespectful and rude, not to say the lowest, crudest, ugliest, low-cognitive effort form of negotiating. Negotiating to me is another communications channel conveying valuable information about how your culture reacts when the stakes are high, time is short, and actionable information sparse. Just like in a critical production down outage.
When bullying in business is your SOP, the network effects of positive collaboration powered by increasingly pervasive technology advancing upon us will deliver fare more attenuated benefits to you than your competitors.
I worked for a guy who had built a business from his kitchen table to 90,000 sq ft building employing 100 people.
He was on vacation and met up with a long-time supplier of a material he used in his products, and after dinner one night the supplier told him he'd be increasing his prices by some large amount. They had a huge argument, and as soon as he came home he started a new plan. He'd make the material himself.
He found a person with a Phd in that field, bought the necessary equipment, and started producing his own polyurethane foams. After another 10 years, he found his own customers and was making more money reselling the foam than he was using it in his own products, and ended up selling the company to a chemical conglomerate for tens of millions of dollars.
Another fun fact: this guy would do all of his drawings in Microsoft Paint. Architectural drawings, product designs, everything. Blew my mind. He would fly tutors in for the week as he tried to learn AutoCAD, Solidworks, etc, but he hated them all.
Suppose I go up to some person I know and say "Give me $100!". They politely decline. I become aggressive and shout and swear at them. Eventually they give in, as a result of which I am $100 richer and they are $100 poorer. I take it we can all agree that this is not reasonable behaviour. (Perhaps it's even criminal; I guess it depends on the exact nature of my shouting and swearing.)
I don't see how such behaviour becomes any better when it's done in pursuit of corporate gain rather than individual gain.
You might say: ah, but it's understood that this sort of thing is part of the game: it's just what happens when people negotiate with one another. Maybe that's true, but I don't think that's any justification. In some cultures it's been "part of the game" that if two men both fancy the same woman then they fight one another and maybe one of them dies. In some cultures it's been "part of the game" that if a man dies his living wife is burned to death on his funeral pyre. Something can be customary but also harmful.
Sometimes you hear people talking about what an awful thing "capitalism" is. That's not a popular sort of opinion around these parts, but I think this is the sort of thing that fosters such opinions: the idea that nothing can be really bad if it is motivated by the search for profit. To hell with that. Yes, some things motivated by profit are bad. And yes, from what you say your father's co-worker's behaviour was one of those things.
My father once worked at an electronics contracting firm. One of his co-workers who was in charge of purchasing parts was masterful while on the phone with suppliers. He drove a very hard bargain and often shouted and swore at suppliers to extract the best prices. Bullying or business?