How can I explain the matter of belief and disbelief without offending?
As Salaamu Alaikum,
You can choose the pattern of ‘exchanging ideas’ with another person (on this topic), without looking as if you want to condemn what they believe in. You can hear what they have to say about their beliefs, and then present the true message of ‘belief’ with rational proofs and with the message of the Holy Quran. In this approach, you will be able to show the truth of Islam and invite others to the right path, without offending anyone.
And Allah knows best,
Mufti Waseem Khan