Is this guy for real? Not single?

Hello Readers, Linda here. Today I want to talk about a guy on PlentyofFish.com. He sent me a message saying he would really like to meet me but he is not single. He's just looking for a little excitement he says and then asks me if I'm ok with that????..seriously dude? Even if you were Brad Pitt and married ( which he just got married by the way) I still wouldn't go there. That's the problem in this world today no one takes marriage or committed relationships serious anymore. At least that's my experience on the Online Dating sites.
I will meet someone and then we start dating and he's still "Online now"all the time! This has happened to me more than once. I just don't get how anyone has time to date more than one person at a time?
Please help me understand I mean I get it if you are just dating and trying to find the right person but if you start dating and become intimate then from a woman's point of view that kind of seals the deal and I don't think either one of you should still be on the site.
This is Exactly why you shouldn't be intimate with someone until you are in a committed relationship. Feelings get hurt and hearts get broken.

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Xoxo, Linda