I thought he was a friend and feel betrayed by his sneaking behavior. People who date are shopping around. I do have a problem, however, with someone who is not honest about his other interests. If he deliberately misled you, you now have a snapshot into his character. This should be a major factor in choosing, in choosing and keeping friends.
Relationships can downgrade or upgrade depending on a variety of factors.
One can continue to have a more casual relationship with a person one once thought was a closer friend. Dear Mrs Web, I went out to a film with an old female friend from college who was in the area for a few days. Afterwards we went to a local brew pub and met up with several other friends. My old friend has been mad at me for leaving her at the pub with our friends. She chewed me out and has cancelled our Thanksgiving plans.