“Injustice is relatively easy to bear; what stings is justice.”

In the context of the Ireland of Thomas Moore's time this is wrenchingly poignant.

So we are supposed to 'bear' injustice? Tolerate it? No way. 'Justice' is supposed to sting, and correct an injustice.

He's talking about the brand of "justice" doled out the Irish by the British during his lifetime.

lol and way to true in today's U.S. In the U.S. today, we suffer the injustices of (by founder's deffinition) a 'national establishment of religion', the Patriot Act, compelled compliance, license, theft of the noble labor's fruit, lying police and politicians, etc.

Mike's got it right.