"could have behaved" is talking about possibility in the past. "could behave" is talking about possibility in the present, or general possibility (at any time). In your sentence there is no significant implied condition.
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"could have behaved" is talking about possibility in the past. "could behave" is talking about possibility in the present, or general possibility (at any time). In your sentence there is no significant implied condition. In your sentence both "could have behaved" and "could behave" are possible, depending