Update: The letter was published on February 11, 2015.
The European nations (Germany, France, Poland, Balkan countries) most affected by the impact of the conflict between Ukraine and the separatist forces are strongly opposed to the prospect of the United States providing "lethal armaments" to the Ukraine-government forces. The voices in Congress urging lethal arms shipments are, in the main, the same as those who gave full-throated support to the U.S. invasions of Iraq and Afghanistan, as well as to aerial strikes in Pakistan and various African nations – and of course we know how successful those armed incursions have been.
The reaction of European nations is that providing arms to the Ukrainian government would be "pouring fuel on the flames," and those nations – closest to the possibly resultant fireball – should be heeded. Indeed, there are ongoing negotiations to tamp down the dispute, and these should be encouraged, not undermined by supply of arms to either side.
Accordingly, Americans' reaction should sanely be, Why do the voices of American politicians for armaments and military force be given any attention, any credibility? The simple answer is they should not, as they shouldn't have been before our previous armed interventions.