I love the meaning behind this, but this isn’t scientifically true
People find killing cockroaches socially acceptable and even rewarding (those who do are seen as brave or helpful) because cockroaches are pests. They spread pathogens, eat food, damage furniture, clothes, and other objects when they find somewhere to lay eggs, and contaminate food and surfaces with bacteria such as salmonella, e. Coli, and staphylococcus. Their saliva and feces also contain allergens that could cause rashes, and in severe cases breathing issues.
Butterflies, on the other hand, do not transmit any disease that affects humans. On the contrary, they pollinate flowers and fruits, supplying us with a food and medicine source. While their larval stage as caterpillars could be considered pests, they don’t damage plants nearly as much as other pests such as locusts which come in unbelievable numbers and eat much more. A more apt description for caterpillars would be pruners, as they only eat small amounts off of the tips of leaves.
So in conclusion, no, cockroaches are not hated because they are “less aesthetically pleasing than butterflies.” It is because they are objectively harmful in many ways, and are considered pests in no exaggeration. While butterflies do next to nothing to harm, and killing them would have no purpose or positive impact.