In February 1798, he asked his Presbyterian congregation, next to Mount Stewart, then under armed guard, and with tenants withholding rent, why Ireland was at war. It was, he observed: "in consequence of our connection with England", and maintained that a French invasion threatened only the government and not the people. Together with uncertain evidence of consorting with the rebels, this was sufficient to have Porter condemned for treason.
In February 1798, he inquired of his Presbyterian congregation near Mount Stewart, currently under armed protection and with tenants refusing to pay rent, why Ireland was embroiled in conflict. He reasoned that it stemmed from their association with England, and argued that a French invasion posed only a threat to the government, not the populace. This assertion, combined with dubious evidence of collaborating with rebels, led to Porter's condemnation for treason.