Whether you've been negatively affected by a group of individuals or not Worra it doesn't excuse demonising an entire minority group. These threads never end well because, for some reason, categorising and demonising gypsies and travellers is the one type of discrimination that is still socially acceptable. It's one of the few areas where MN-users find themselves agreeing with Top Gear (see the recent pikeys case). 
And if you doubt that there are generalisations on this thread then substitute gypsies/travellers for black, disabled, any other minority group and you'll see how unacceptable and prejudiced most comments on this thread are.
If people are causing a public nuisance or parked illegally or creating a health and safety hazard then there is legislation in place to deal with all those issues. If your local authority or police fail to implement that legislation then that is an issue you have to raise with them.
As for the comment that 'they should just buy land and live there'
- A lot of travellers do buy land and do live there
- There is no inherent planning provision for residential caravan sites. If you meet certain criteria you are almost guaranteed to secure residential planning or commercial planning but planning permission for residential caravan sites is not protected in this way
- planning applications for residential caravan sites are the only planning applications where you have to include the ethnic group of the people who will live there. If you build houses, you don't need to specify. If you build a caravan site, you have to say if it's for travellers. It's enshrined bigotry.
And before anyone asks, yes I've lived beside travellers. Yes, I work with them to provide support and help them through lots of these processes. Yes, I think they have a right to safe, stable housing; access to healthcare and education.
It's also worth pointing out that bigotry against travellers isn't a victimless crime. In the last decade, bullying of traveller children has increased to levels not seen since the 1960's.
Perhaps it is time for MN to consider a campaign promoting tolerance and awareness.