Yes, but under the doctrine that the enemy-of-my-enemy is my friend: The fact that those Poles were willing to kill German's meant that they were useful allies. Killing Poles was therefore counter to the Soviet Union's immediate goal of defeating the Nazis.
After all, we managed to overlook the communist threat in an effort to defeat the Germans, even though there was ample evidence of German-Soviet cooperation prior to 1941.
Certainly, but Stalin was looking to the long-term. He knew the war was in its final stage and that Soviet victory was inevitable by the time of the Warsaw uprising. Furthermore, he did not care about the fact that his decisions might lead to more Soviet casualties. He saw a potential threat to his post-war domination of Poland and decided to let the Germans eliminate the problem for him.
He saw the situation as part of a greater war- the war against class enemies of communism.
Roosevelt and Ilk were commie sympathsizers, no surprise here.