There are two parts to the plans for Internet intercept support in the UK, the police and the security services. The police use is primarily for the purposes of stopping crime. The purposes for the security services are opaque and unlimited as long as they are for 'lawful purposes' - i.e. anything under the Intelligence Act 1994.
When opposing this it's important to understand the remits of the two organisations and that one is nominally accountable to the public, while one isn't.
I am much less worried about letting GCHQ trawl my traffic data than I am letting my local council noodle around in it. Mostly because GCHQ probably already do it - they certainly have the capability, but also because local councils have shown themselves to be corrupt and "data-leaky".
I'm not bothered about my traffic data being trawled. I oppose this bill because it's stupid - the people who have to keep data are not clearly defined; hiding some of that data is trivial for criminals; keeping that data is an unreasonable burden on some (but not all?) ISPs; etc etc.
It's frustrating that there are some really clueful politicians and advisors, yet governments keep pumping out really stupid laws about computers and networking.
When opposing this it's important to understand the remits of the two organisations and that one is nominally accountable to the public, while one isn't.