All you need is a good rationalization. Here's an example: The world's not ready to give up meat. If I were to stop consuming animal products, I'd implicitly be saying my behavior is morally superior to those who do. That's elitism and there's nothing more repellant to the progressive sensibility than elitism. By continuing to consume animal products like everyone else, I'm declaring my solidarity with the rest of the world and only through solidarity can we affect change.
Here’s another one: The history of social movements proves change can only come gradually. If I were to stop consuming animal products all at once, I’d be violating this most basic truth. Justice takes time. Today, I’ll shake my head solemnly at what the poor creature I’m eating had to endure before it wound up on my fork. Tomorrow I’ll sign petitions giving them a few extra feet of cage space and someday in the hopefully not too distant future I’ll stop eating them.
Gradual change also works better for the animals. Animals are creatures of habit. Sudden change to their routine can upset their equilibrium. To go from the horrific treatment of factory farms to not being slaughtered at all would be too big a shock to the system of these poor creatures. They need a transitional phase, half way between factory farms and freedom, where we continue to slaughter them but do it in a more humane way. After they’ve grown accustomed to this more humane slaughter, only then will be they be prepared for the next step of emancipation.
Those are just few examples. So if you’re deeply, passionately concerned about the plight of farm animals, but you don’t want to give up the delicious taste of their flesh, don’t worry, there’s so many rationalizations out there. You’re sure to find one that works for you.