It was canon for quite a while that Clark actually loved both women more or less equally (there was one 'imaginary story', in fact, where he splits in two, and they're like 'yaay! Our problem's solved - there's one LL for each of us!'). Lois was more in evidence in his daily life, and therefore more of a factor, but Lana was his childhood sweetheart that he never quite got over - and given that he stayed loyal to Lois right until her death and for several hundred years afterwards, I wouldn't exactly say this is sullying her memory or anything like that.