If I had not shared the files with you, and they cannot be found in a public database, then the only way you could have obtained my files is through illegal means, such as breaking into my house or planting malware on my computer. In that case, the issue of sharing those files is beyond the point, since you already invaded my privacy and broke the law.

If I had shared a file with you, however, then you should feel free to share it with others as much as you'd like.