The reason why I would not approve of this is that if you have the ability to time travel like that then why go straight to killing? Why be savage like that?
Like, it would be just as easy to render him impotent or out of the picture without killing him. You could, for example, take him back to the future with you (assuming you can return) or prevent his parents from meeting, or something. There are many possibilities here.
Depending on your resources and abilities (which, coming from the future, are likely to be significant), you could even try to tackle the root issues that created Nazi Germany and its allies, which would be much more beneficial and likely to prevent fascism than just killing Baby Hitler and declaring your job done.
This assumes time travel is not horrifically immoral to begin with, which depends a lot on how time travel works. Does it create a new world, or does it cause 6 billion people who exist now to never be born? Also, so far this timeline has avoided global nuclear war.