Let's face it... the US and EU do not have quite enough invested in the Ukraine to actually commit any sizeable resources to solve the situation purely for Ukraine's benefit. This petition is to focus attention on the ancillary benefits of doing so.
This is an opportunity to put an end to Mr. Putin's aggressive tendencies. Having already taken the Crimea with a minimal response from western powers, he is emboldened to break off a chunk of Ukraine as well. Allowing this would not bode well for peace in that part of the world. A forceful response however would easily put an end to such fantasies, and deeply embarrass Putin at home, potentially putting a permanent end to his adventurism. This is a worthy goal, and would seal the Ukraine as an American ally on the border of Russia.