To what extent is it just for some Muslims to describe Western peoples as "infidels" (kuffar), given that the call of Islam has not been conveyed to them with wisdom and good admonition? And is describing them as "astray" (dalleen) more appropriate in this case? And what is the responsibility upon Muslims for not delivering the message in the best possible way?

Describing peoples as disbelievers is appropriate if they are so, and the responsibility of conveying the message falls upon everyone who is able to do so. It is not a condition for the preacher to be full-time. The preacher can introduce Islam through media, and whoever knows Islam but does not accept it is called a disbeliever (kafir). It is unlikely that there is a people to whom the message of Islam has not reached. As for those whom the call has not reached, they will not be punished until after the establishment of proof, and they are not described as disbelievers or believers; they will be tested on the

Day of Resurrection. Whoever hears of the Prophet but does not believe in him has no excuse and is among the people of the Fire.