Inequality exists because some people have more opportunity than others, which starts early when some people simply work harder in school than others. Some people get into better universities than others. Some people get into better careers than others. This is always going to exist, regardless of who gets taxed more. If you believe simply taxing the rich is a solution to a societal inequality that has always existed and will always exist then you fail to understand the nuances of the subject.
One point I'd also make is that in the UK the top rate of tax got decreased a few years ago and revenues actually went up. Taxing people into oblivion is a surefire way to reduce tax income.