When a rov questioned the point of convincing congregants to buy kosher when their kitchens were treif, the Rebbe explained that it was the first step: helping them realize that kosher food tastes good too.
Reb Binyomin Klein related:
A rov of a far-flung town was once in yechidus. Of the various communal matters, the Rebbe focused on the kashrus situation in his community. “It would be advisable to begin a campaign in your city, encouraging people to purchase kosher food,” the Rebbe said.
The rov was perplexed. “Rebbe, what would we gain with these people buying kosher food?” he asked. “Their kitchens are treif anyway, so once the kosher food would be cooked in their kitchens, it would also become non-kosher!”
But the Rebbe explained to him that the problem is a deeper one, “In your city, the general perception is that kosher food doesn’t taste good. Once people are introduced to kosher food and see that it is tastes good, they will realize that it is not that different from what they are used to.
“Then,” the Rebbe continued the elucidate the strategy, “once they begin buying and eating kosher food, it will be much easier to inspire them to kasher their kitchens.”
From The Weekly Farbrengen by Merkaz Anash