We often find ourselves having to do a bit of bad for the greater good. Perhaps you work for a cultured meat company, and so buy meat from an animal to compare it to your products. Or maybe you fly to a conference, releasing greenhouse gases and spending money on travel/housing, when that money could be spent in better ways. Whatever it is, there's a common response to such behaviors: offsetting. 

Offsetting often takes the following form: you spend money on something harmful, so you spend the same amount of money on a charity combatting said harm. Much of the time, when people talk about offsetting, they see it as a form of absolution, repentance, etc. "It's undoing the harm I caused."  But is this really the case? I think not.

The money you donated to charity, in offsetting, could've been donated regardless of the initial harm. Thus, it's plausible that you should've donated said money, even if you didn't perform this harm. The harm isn't 'undone' or 'cancelled out of existence' by your offset. It happened, it's done, there's nothing you can do about it. While it's true that a donation can do an equivalent amount of good to your harm, but wouldn't it have been better to do that good without the preceding harm?

It's not my intention to tell people not to offset: I'd rather you offset than not. Rather, I want people to change the way they think about offsetting. If you can already afford to donate that extra bit of money, then donate it. And if you're unsure about doing something wrong for the greater good, don't let the thought of offsetting bring you too much comfort. You're still enacting harm in the world. Sometimes we need to do something bad, I won't deny it. But there exists a threshold for how bad a thing we should do for the greater good, and offsetting shouldn't encourage us to raise that threshold.