Hamlin spoke during a national conference call Tuesday, two days after a brawl between Keselowski and Jeff Gordon on pit road at Texas Motor Speedway.
He said the consensus among his peers was Keselowski didn't have enough space to attempt a pass of Gordon in the closing laps of Sunday's race. Keselowski's bid to squeeze his car through a gap between Gordon and Jimmie Johnson after a restart led to contact between Gordon and Keselowski, which triggered a postrace fight that left both drivers slightly bloodied.
"I think the challenge a lot of drivers probably have right now with Brad is there's no remorse," Hamlin said. "He has the right to feel the way that he feels -- but when there's no accountability ... they're going to be upset with you.
"It's tough to win a championship if nobody likes you. That is going to be a very, very tough task."
Hamlin and Keselowski infamously feuded for three seasons, and it came to a head in 2009 when they tangled repeatedly on the track in the Nationwide Series. Hamlin complained repeatedly that Keselowski refused to engage in reasonable conversation about their incidents.
The two raced incident-free for many years and had their first major scrap last month at Charlotte, where Keselowski lost his cool following the race. Hamlin had to be restrained from confronting him, and Matt Kenseth jumped Keselowski from behind in the darkened garage.
Keselowski was fined $50,000 by NASCAR for his behavior, but Hamlin and Kenseth went unpunished.
Keselowski then overcame a week of criticism from his peers to win at Talladega and advance into the third round of the Chase for the Sprint Cup championship. And Sunday, Keselowski used an aggressive move on Gordon to try to win the race.
It led to contact with Gordon that caused the four-time champion to spin after his tire went down. Gordon went from racing for the win to a 29th-place finish Sunday, and he confronted Keselowski on pit road. Kevin Harvick shoved Keselowski from behind, which triggered a brawl between the teams and drivers.
"You're just looking for someone to say, 'Man, I'm sorry I ruined your day. I screwed up. I apologize,'" Hamlin said. "When that doesn't get said, then it immediately lights a fire in your stomach that he doesn't have any remorse. He's just like, 'Oh well, it's your problem.'
"That just lights a fire in your inside. Especially when you just had a bad day and your season could have rested on that. That really set things off. If Brad would have talked to Jeff, and said, 'Man, I was going for a hole, it was my only chance, I'm really sorry it cut your tire.' Instead, it was, 'Oh well, sorry, buddy. You left a hole.' If he did that to me, I would have had the same reaction as Jeff. No question."
Hamlin has a sense of the feelings in the garage because he's part of a group text message chain of 20 drivers, one of which is Keselowski. Twice on Tuesday he referred to "a common feel amongst drivers," including the sentiment that the hole was not large enough for Keselowski to try to squeeze past Gordon.
"People are calling that a hole, that was a very small hole," he said. "It was not enough that a car was going to fit without being in contact with Jeff. Somebody was going to have to pay the price. It was Jeff Gordon. And it made him have a bad day."
Gordon, who before the restart was headed to a victory that would have earned him an automatic berth into the Nov. 16 championship finale, dropped to fourth in the Chase standings. Only four drivers will race for the title, and Keselowski is seventh in the standings with Sunday's race at Phoenix remaining to set the field.
To advance, Keselowski (who has a series-best six wins this season) either needs to win at Phoenix or have a strong run Sunday while other contenders falter. But Hamlin, who goes to Phoenix tied with Keselowski teammate Joey Logano for the points lead, believes Team Penske is strong enough to help Keselowski overcome the adversity and still win the title.
But he questioned if it will be worth it for Keselowski, who has increased his list of adversaries this season.
"If you ask me do you want a championship trophy or do you want the respect of your peers, I will take the respect from my peers because that trophy, they can't put in my casket," Hamlin said. "What's the fun of a NASCAR [championship] party that nobody shows up to?"