Sanchez has been well received by the manager for his attitude a couple of times if I'm not mistaken. He also kept quiet about exits publically and said he regrets nothing (even if he did from a footballing perspective).
That didn't stop him from being unceremoniously kicked out of the club at the end of the window did it. So what is your point?
Rashford never publically went out and spoke about Barcelona. How is this in any way comparable to Lukaku?
No he just got his agent to do it for him which is even more snide.
What difference does the method of which they declare their interest in leaving make? If they do it nicely it's ok, but if they do it in a back handed way it's more respectable?
Pogba is a good example. I really am not a fan of Pogba the player but his professionalism was highly commendable, even though he's a far bigger brand than Lukaku. Yeah he said he wanted a new challenge but that's hardly disrespectful. He never openly spoke about Real Madrid and wanting to play in La Liga that summer. Lukaku did the opposite. He literally said he wanted to go to Serie A and he wants to play for Conte that summer. Then he started pissing off teammates before being forced to train in Belgium.
Now tell me what is so disrespectful and different from Lukaku praising Juve and saying one day he'd like to play in Italy, to Pogba's comments about needing a new challenge as if he's won all there is with the club?
Let's compare
Lukaku;
''Juve have a great project in place and they just keep going. Every year they try to get stronger.
"Without doubt, Juve are one of the two or three best teams in Europe. They've got a great coach on the bench and extraordinary players in every area of the team.
"Cristiano Ronaldo stands out, but watch out for the others too. Paulo Dybala is already impressive and getting stronger, while I love Douglas Costa''
Pogba while contracted to club as you stressed with Lukaku;
''For me I have been for three years in Manchester and have been doing great; some good moments and some bad moments, like everybody. Like everywhere else.
“After this season and everything that happened this season, with my season being my best season as well... I think for me it could be a good time to have a new challenge somewhere else
You're clutching at straws if you want to complain professionalism from Rashford and Pogba to Lukaku.
So because Pogba said he rather a challenge some else but United, that's more respectful than Lukaku praising a team in a different league?
I think it's you that's clutching at straws trying to put levels on how a players declares their intention on leaving for another club when while acting as if Lukaku crossed a line when praising Conte, failing to mention Pogba actually met up with Zidane, but that's ok because he's a bigger star so he's not unprofessional in your eyes.
And it's ok for Rashford because he did it through his agent