Final answer:
Abolitionists would most likely support the resolution passed at the 1851 convention criticizing the Fugitive Slave Law as unjust and cruel, as their goal was to end slavery and oppose laws enforcing it.
Step-by-step explanation:
The group that would have been most likely to support the resolution passed at the convention in New York in 1851, which expressed opposition to the Fugitive Slave Law and its enforcement, would be abolitionists. This group, consisting of individuals and organizations dedicated to ending the institution of slavery, would view the law as a moral abomination and an extension of slaveholder power into the free states. Conversely, groups such as slaveholders, Southern Democrats, and most factory owners would likely oppose such a resolution due to their interests aligned with maintaining or benefiting from the institution of slavery. The abolitionist movement was driven by a combination of moral conviction and a belief in the injustice of slavery, with many adhering to the principle of civil disobedience against unjust laws such as the Fugitive Slave Act.