You are right. he turned politician when people tried dirty politics aganist him and thrown him out of the team unjustifably. many great players have earlier been out of form, even in the present Team India that we see, but have never got a treatment like Ganguly got.
So, he has every right to defend himself.
If he have to indulge in politics, it is because a section of mindless people have done dirty politics on him.