Rory McIlroy says competing against LIV Golf players at the upcoming BMW PGA Championship will be "hard for me to stomach".
On Sunday, McIlroy became the first player to
win the FedEx Cup three times with victory in the Tour Championship.
The Northern Irishman - one of the Saudi-backed LIV Golf series' fiercest critics - reiterated his stance after claiming the PGA Tour's richest prize.
"I hate what it's doing to the game of golf," McIlroy said of LIV.
A number of high-profile players have left the established tours for the £1.6bn LIV Golf series which is holding eight invitational events in 2022 with a prize fund of £200m before turning into a league from next year.
Major winners Brooks Koepka, Phil Mickelson, Bryson DeChambeau and Dustin Johnson are among those to have joined, and the PGA Tour responded by indefinitely banning those players.
However, DP World Tour players who have joined the fledgling circuit will compete at the BMW PGA Championship at Wentworth after their
suspensions were temporarily lifted in July.
Lee Westwood, Sergio Garcia, Graeme McDowell and Ian Poulter are among the LIV players expected to feature at the DP World Tour's flagship event from 8-11 September.
McIlroy added: "I hate it. I really do. It's going to be hard for me to stomach going to Wentworth in a couple of weeks' time and seeing 18 of them there. That just doesn't sit right with me.
"So yeah, I feel strongly. I believe what I'm saying are the right things and I think when you believe that what you're saying is the right thing, you're happy to stick your neck out on the line.
McIlroy captured his third FedEx Cup following a thrilling final-round duel with world number one Scottie Scheffler at East Lake in Atlanta.
Scheffler started the week with a six-shot advantage over the four-time major winner as players began the season-ending event on staggered scores, determined by their respective positions in the FedEx Cup standings.
McIlroy also started the final round six adrift of
Masters winner Scheffler but carded a closing four-under 66 to beat the American and South Korea's Sungjae Im by one shot.
"Look, it's been a tumultuous time for the world of men's professional golf in particular," said McIlroy, 33.
"I've been right in the middle of it. I've picked a great time to go on the PGA Tour board.
"But yeah, I've been in the thick of things. I guess every chance I get, I'm trying to defend what I feel is the best place to play elite professional golf in the world.
"It's in some ways fitting that I was able to get this done today to sort of round off a year that has been very, very challenging and different."
McIlroy will follow his first BMW PGA Championship appearance since 2019 by making in his debut in the Italian Open at the end of September at Marco Simone Golf and Country Club, the venue for next year's Ryder Cup.