This blog is good advise and it's true that you need to filter the good ideas and the bad ideas in a forum. It isn't something easily done at all and users can give ideas that really spoil the next version or release of your software. But that doesn't mean that you should ignore ideas.
I personally feel that it is a balance between visiting a forum and taking in ideas and criticism and trying to stay focus and true to your project goals. It is very hard to give a sweeping statement like 'don't visit the forums'. No... it's a sweeping statement in anyway and too extreme. I would still advocate visiting the forums to find some ideas but it's up to the project leader to balance the fulfilment of ideas from users and the main project goal by retrospection and self understanding.
If people have something personal and negative for their hate messages... all you do is smile at them and leave them as they are or if you are an admin, you simply ban them and remove their messages for the act of committing personal insults.
Things like feature requests and bugzilla are for submitting bugs and feature requests anyways. These are the places bugs and features requests should go... rather than forums.
In the arts of Knowledge Management in IT, forums is a good place to find ideas but because it's a place that is rather 'fuzzy' it can be a 'love-hate' affair. It is nevertheless a place to go but it all boils down to attitude, goals, principles.... things that manages the person who drives the project. The people out there can say all the want.. helpful or not helpful stuff... but it is the people in the project rather than the people sharing their ideas that matter when it comes down to project planning and design.