but treating others unfairly for impersonal reasons is unjust.
Um, so is treating them unfairly for personal reasons. In fact, inasmuch as "unfair" and "unjust" can be read as synonyms, treating others unfairly will always be unjust.
This quote from Mahatma Gandhi clearly reflects the previous point.
No, actually, it doesn't. It shows that democracy need not be tolerant, and that the intolerance of a democratic nation can be just as bad as the intolerance of a tyranny (though I'm not sure that even that was Gandhi's meaning). It makes no sense at all if one believes that tolerance is innately a part of democracy, as then the notion of democracies engaging in oppressive warfare would be foolish.
When one takes advantage of another's weakness, intolerance is demonstrated
No, again. It may indicate power lust, but not intolerance. If I decide to steal the wallet of a man who has collapsed on the street, for instance, then I am greedy, dishonest, and ruthless, but I am not intolerant.
a global community tolerance must be practiced to its fullest extent
Should we tolerate people who don't believe in tolerance? Because most cultures don't. The belief that one's own culture is superior is as fundamental to most cultures as the urge to fight to live is fundamental to most animals. Men may embrace tolerance in much the same way as they commit suicide, but in neither case is the condition natural. You could of course try to spread the idea of tolerance to all, but to do that, you would need to spread the ideological underpinnings of the notion of tolerance, too. In other words, you would have to subjugate everyone to a single set of core beliefs.
Overall your essay isn't very well thought out, logically speaking. It expresses the right sentiments, though, so I imagine you'll do okay.