I can think of several projects where clearance of Brutalist architecture was a prime motivator for redevelopment. The demoition of the Tricorn Centre in Portsmouth is one, the plans to demolish Birmingham Library another.
Having said that I don't think Brutalism as a style is automatically ugly. Preston Bus Station, while fairly run down is an attractive building as car parks go, the National Theatre is certainly striking and very attractive inside, the Barbican is a bit of a unnavigable mess, but from the garden side it's actually quite pleasant and many people love it. And therein lies the problem with 'aesthetics' based demolition; who is to say what ugly is? If something is falling apart, serves no economic or social purpose or encourages crime or anti-social behaviour then you can make a fairly strong argument to remove it. But if a building works to the function for which it was designed, but is just considered ugly you will still find some people who love it, and why should one view of ugly be taken over another?