There's a lot of very cocky people on here trying to justify their poor behaviour behind the wheel - and I'm not talking about the nervous drivers (who can be dangerous, certainly, but are not universally so).
You absolutely should not be driving to the speed limit plus 10% - speedometers do not always under-report your speed, and if you're doing this, you're almost certainly speeding, at least some of the time.
If you're driving "to the speed limit" as a principle, and tail gating, or overtaking other road users dangerously to do that, you're driving dangerously. There are many, many roads where it is dangerous to attempt to drive at the speed limit, even when conditions are otherwise good. These are usually rural roads, which are often NSL by default, not because it's remotely appropriate to drive at 60. Not that this fact stops the occasion idiot attempting it.
Even where the road is safe to drive at the speed limit, there is no excuse for tail gating - you can never know why the car in front is driving more slowly that you'd like, and, even if they're doing something stupid, dangerous or just annoying like being nervous on a new road, that is no excuse to try and bully them into speeding up. You could equally be held up by an accident, traffic, a tractor in the road (or any number of things), so you'd be better off leaving yourself more time, so you can allow other people to drive less quickly without it affecting you.