The kind of GM who is married to having to roll for stats is probably not going to care about bad dice rolls causing an ogryn to have low toughness and strength scores. If they do care about one but not the other, that is a good place to try convincing them of the error of their ways when it comes to randomly rolling stats.
The basic argument is:
"Does it seem right to you to roll a die once at the beginning of the game that gives you +10 or -10 to every roll you'll make in the future? Because that's what random rolling for stats is."
If the GM wants new players to quickly generate characters, I can see doing random rolling, but the players should be allowed to go back and do point buy after they learn the game a bit.
If a GM thinks it's more fun for character generation to be unfair and forcing people to play what they roll, make the above argument and consider a different GM if it doesn't work, because they may have an incurable case of grognardia.
I have a pretty bad case of grognardia and I'm not that hardcore. Even if I was running a campaign where the predominant Chargen method was random gen, If a player presented me with a well thought out character concept I would probably go with point buy. It make no sense to be thinking of playing a highly intelligent academic and ending up with Jet li the assassin!