Liverpool fans should not dare call Sadio Mané a traitor or even boo him if he play against Liverpool because Liverpool didn't give him what he deserve. Even Roberto Lewandowski that is given what he deserve at Bayern Munich said he's leaving, his mind isn't at Liverpool again. It doesn't even matter if Liverpool fans boo Mané, he has got another fans at Bayern Munich and football contract isn't about how much you love the club because the club would just use you and dump you, you need to be selfish at times if you want to have enough to spend after you retire at work.
Liverpool really fucked themselves up concerning Sadio Mané's contract, they watched him playing for 5 years without sitting him down and add more to his contract, even if he would later go at the end, his price won't be as cheap as they bought him now because he worth at least sixty million pounds if his contract remain at least two years due to the form that he is. He can play in both two wings (both left and right) he can play at the midfield (if coach like Joseph Guardiola or José Morinho have him) and he can play at the centre attack (his new position at Liverpool) and he don't have injury, only if coach just choose to rest him.
Bayern Munich has already used Roberto Lewandowski finished, so they shouldn't even stop him from going, he has already spent good eight years with them, they didn't play with his contract like Liverpool did to Sadio Mané, Bayern Munich made Lewandowski sign more contract before the current one lapse. One fifty percent salary increment addition is what Sadio Mané got at Bayern Munich, he works high and pays low, but now he'll earn high with his high work because he's not a player that gets tired and manage himself, he plays with everything he have.