Let me try to sum up my feelings:
You can argue Kidd had it coming: From the prior clash with Beckmann, from now being worth 3 billion, whatever.
But Bartolomeo was *way* out of Shanks' league, and he passed the loyalty test by instantly swallowing the poison.
So, Shanks, who is supposed to be a better father to Luffy then his actual dad, encounters a overzealous supporter of him who is totally out of his depth. He could have just let the kid run, but chose to try and kill him anyway.
That is what I am up in arms about. As Shanks is now no better then Teach or Kaido or Big Mom, just another arrogant, cruel warlord throwing his weight around.