No, there are famous gay pop stars now. Sam Smith is a prime example, people LOVE him (except here on ATRL). Troye Sivan's fanbase is made up of mostly straight girls and gays and he's doing great right now. There are others but it's mostly in the acting world where it's seen as acceptable.
I think there are two routes that I see working for singers right now: 1) be perceived as straight until you make it big, then come out but keep your music ambiguous to continue to appeal to the masses (Sam Smith, Frank Ocean, etc) or 2) be out and obvious from the very beginning and make it big off your core fanbase, allowing the rest of the GP to follow suit.
These days, as long as you aren't campy and aggressively forcing it on people like Adam Lambert did, I think you'll be good. Being LGBT tends to make you more popular these days, unless you're black.
