What is the stand of leftists and liberals on celebrating valentine day?

it is not our culture, similarly it is not a communist culture and it is a culture of the capitalists, no doubt. But, i don't think communists would encourage these mad things. why ? i respect them for their good and strict ideology and principles which always aim on poor, down trodden and surely not on lazies and uncultured ones. As you pointed out, it is the culture of capitalists, and therefore no regards from leftists and liberals, i think.