I don't want to be mean, rude or offend you, but I really wanted to say this here. So, don't take it the wrong way; I just want to say the following to make you see some things.
When I talked about people tricking the Cup draw (including you), you said the game is not a sportsmanship one. Another thing you said or someone else said: it is a strategy. In other words, you and some others defended a bad thing because you and them did it too. But then, what is the problem with someone else (intentionally or unintentionally) supported against you? It can be said that this is a strategy too or that the game is not a sportsmanship one.
What if all those victims of your Cup draw manipulations and other manipulations or of others or of their other unfair ways like using other accounts to support against a team start opening threads similar to this one, post pictures of you and others in the process and say similar things that you have said above. It is even more annoying for those victims that faced teams significantly stronger because the managers of those teams manipulated the draws. You are complaining about something that has no significant effect when you yourself have been doing unfair things that have much more effect.
All this comes to one thing that I said: some people will never realise what is bad in what they do until they become the victims of those things themselves, and even then, some people will not realise.
Now, coming to the subject itself, I was never a fan of unfair things. But, you cannot say for sure what he did there was intentional. He might have been friends with the other managers involved too, and he clicked on the other side instead of yours. Some people also don't know that they can watch a match without supporting any of the two sides involved. Also, everyone can make mistakes, it is not a matter of age. If it was intentional, then this was bad from him, but he might have seen it more other way, that is, it is more of strategy for him.