Compassion remains important. Likely the vast majority of people who eat meat are doing it purely out of habit and have had no exposure to other ways of thinking or being. They aren't trying to do harm, be evil, or murder anything. They are unaware. They are uneducated about the food system, the intelligence of animals, etc. To accuse them of being heartless murderers will just drive them away and validate their assumptions about "militant vegans." Thus validated, nothing will change. If you want to change the world and change people's thoughts and habits, it takes middle ground compassion, tolerance, negotiation, and patience. Abolitionism, though I definitely have sympathies with it, doesn't usually work.
Though not a perfect analogy, the abolition movement did not stop slavery in the United States. Many considered abolitionists extremists. Abraham Lincoln did not publicly advocate for abolitionism. If he had, his own party would not have made him a presidential candidate. He took a middle ground and ultimately succeeded, though not without controversy, in abolishing slavery. Yes, it took a lot of horrific violence and many people suffered during the interim. But slavery did end (the horrors of Reconstruction are another story). An abolitionist candidate would have lost the 1860 election and likely allowed slavery to continue longer. Lincoln wasn't a perfect human being, but he was a savvy politician. Veganism doesn't need a John Brown, it needs a Lincoln.
And to say that compassion and patience will just lead to more suffering, there is truth in that, but I also don't see abolitionism as accomplishing anything but prolonging the status quo indefinitely. I'll take potential temporary suffering over potential prolonged indefinite suffering. If the goal is to actually get people to stop consuming animal products, more of a middle ground is needed. Compassion is vital.