Put yourselves into the shoes of the Russians in this case - the United States' supplying Ukraine with military equipment would be very similar to Russia's sending tanks and their Kalashnikovs to Mexico, had the latter been anti-American. Recall the Cuban missile crisis... we are getting to a much worse situation now - Cuba (or Mexico) for the United States is not even close to that what Ukraine means, and historically meant for Russia and Russians. If Obama takes decision to arm the Ukrainian government's army that means declaring war on Russia.
We are on the brink of the World War III - one little mistake and we are all doomed. Let this mistake not be made by America - prevent the White House from sanctioning provision of weapons, armaments and/or financing thereof to Ukraine.