You don't. Ireland has plenty of great Irish craft breweries making world class beers, including stouts. Guinness, on the other hand, is a beer owned by Diageo, a PLC based in the UK that actively strives to monopolise the beer market and close down small independent breweries.
Is fearr liom Guinness means "I prefer Guinness".
Is breá liom Guinness is closer to "I love Guinness". aoibhinn is a bit stronger than breá, but it sees a bit much for beer.
Does this help?