I think it depends on the relationship. If you never talked about it, and he considers it cheating, then it doesn't look good. If you had talked about it, I think what you did would have been acceptable in a surprising number of relationships.
Personally, I would worry more about your own relationship than what people on here think about it, though. He thinks it was cheating, and his position is certainly reasonable even if it isn't 100% obvious without a doubt. That means you two should probably work it out between you, with some apologizing, compromising, and learning done by each party.
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