Failure to obey traffic lights results in 2 points and a €80 to be paid within 28 days. I don't think there are penalty points for not having tax and the fine is €60.
FYI, this is what the road safety website has to say about Amber:
An amber light means that you must not go beyond the stop line or, if there is no stop line, beyond the light. However, you may go on if you are so close to the line or the light when the amber light first appears that stopping would be dangerous.
You obviously felt it would be dangerous, whereas the Gardaí in the car behind you felt otherwise.
I would have thought they would have issued a notice there and then. I broke a red light once (accidently if that makes any difference) and was pulled over and issued with the notice there and then. This was pre penalty points though, so things may have changed since.
As for them being on a power trip, well to be frank the more heated things got then the lower your chances of being let off. And to be fair to the Gardaí, finding you driving with no tax (for whatever reason) simply would have re-inforced their stance.
The best thing to do now is let off a little steam, pay for your tax as soon as possible, don't drive the car until it's paid, and see if you can set money aside to be for the fines.