User blog comment:FairyRaven/Fairy Tail Chapter 328: Zodiac, Review and Commentary/@comment-180.194.30.136-20130419132625/@comment-7418318-20130419133425

If the 10.000 Dragons were killed in the present, he could only kill more Dragons by traveling into a time before the dragons timetraveled. And if he killed them there, they wouldn't come into the future, thus voiding the event that made him wanting to go back in the first place, right?

This is getting into the same headache inducing levels as our last discussion about future rogue coming from another timeline than future Lucy :P

Ah Rave was so much more straight forward. X get a cut -> X from the future immediately get's a scar in the same spot.