the Brits and French so conveniently forgot that the Soviets invaded Poland as well.
Nope, they didn`t. Polish British French alliances had a few secret provisions and the main one was that their main enemy was Germany. The attack by the USSR wasn`t taken into account.
If the alliance was only good for one aggressor
Exactly! :):) Poles insisted on recognising Germany as their arch enemy.
Neither the Brits nor the French gave a sh*t about Poland in 1939
Bollox. They declared war on Germany on 3 Sept. If they hadn`t cared, they would`t have done it, right??
As for the final part of your post, you got lost too much so I prefer to abstain from commenting.