This is so wrong, I'm not even sure where to begin. Asking permission/consent to kiss your partner doesn't make you "unsure of yourself", nor is it unerotic. And putting this out there as advice to men is furthering the wrongness that is so patriarchal.
I'm currently spending time with the couple I'm dating, and my boyfriend, who had not 2 minutes prior, been licking my p*ssy, but since we'd changed position, looked into my eyes and whispered, "may I lick your p*ssy more?"
Super hot.
Earlier in the evening, though we had all been kissing and touching one another, he whispered to his wife of over 30 years, "may I kiss you?"
Super hot.
Not a damn thing about any of this asking permission was deeply unerotic.
He asked permission so many times during the multiple hours we were all together and every single time he did it just furthered the heat we all felt between the three of us.
It's all about timing, period.