wombleref - I know where you are coming from, but I agree with Browner : it's the coaches job to level up a game, not the referee's.
You should always ref everything straight, as soon as you start delibrately favouring one side (for any reason, even with the best of intentions) I think you are on a dangerous path.
Also - if it was a league game there's almost certainly a maximum points difference (?) that takes account of the mismatch. In most youth leagues when you get to that, the game ends and the two teams can play on as a friendly. If your levelling delayed / prevented the maximum difference being achieved then you may even have prolonged the agony :-(
Here in Holland, the regulation for youth matches is that if there is 30 points difference at half time, the teams should mix. The side that is losing never wants to; they'd rather play together.
I find it very difficult not to referee what I see equitably, but there is more danger in what I don't see at all than perhaps some leniency towards the end of a game where one side is getting thrashed. Such leniency is not "deliberately favouring one side", but rather being less tolerant of minor technical offences by players on the winning side.
I'm firmly in WombleRefs camp, perhaps not as to detail, but rugby remains a game for me, and games are meant to be enjoyed. My personal enjoyment comes from ensuring as safe a match as I can which sometimes includes making sure the losing side benefits from my accidentally missing something.
My match yesterday had long advantages for high tackles brought back to penalties. The weaker side were the ones penalised for their poor tackling technique. The stronger side probably gave away as many penalties in total, but more for technical offences. Both teams wanted to play, so they did.