실례지만 is not from 실례하다. 실례지만 is a short form of 실례이지만 which is composed of 실례+이(다)+지만 실례 is a noun which means "discourtesy, bad manners" 이다 means "to be" 지만 is a connecting particle means "though" Equally, 실례다 in the following example is a short form of 실례이다. 여성에게 나이를 물어보는 것은 실례다 It is not good manners to ask a woman her age.