Once we form an opinion or make a choice, its inherent human nature to embrace a viewpoint that ignores other possibilities and choices - even the ones we seriously considered before making a decision a certain way.
This helps us not ruminate the "what could have been" scenarios which leads to unhappiness. It takes a strong and secure human to even tolerate the thought that anything other than his or her choice has some merit.
People like sureshs have formed a strong affinity to Nadal (his game, personality, what he represents etc). Others prefer Federer. So far so good.
Now, the critical difference between sureshs (also CMM, TennisandMusic, veronique etc) and a normal fan is like the difference between a person who is a religious extremist vs someone who is merely religious.
In sureshs' world, his fandom is not secure and complete until all other possibilities, however real and valid, don't exist (sort of like the jihadists). Normal people vent and groan about something they don't believe in from time to time, but also acknowledge good when they see it. Extremists cannot stand that. Their whole existence relies on their belief and that no one else can be right. Therefore his idiotic threads like this.