Without having much familiarity with the tradition, it seems that the shahadah, lÄ ilÄha illÄ-llÄh, there is no God but God, can be taken in several different ways.
There is the ethnocentric interpretation, taking the Islamic God as the only one, or rather, the Islamic interpretation of God as the only correct one.
Then, the interpretation of the practitioner or faithful, having God as the single or main focus for ones attention and life.
Or the worldcentric one, seeing God as One, with many interpretations and faiths appropriate to the culture and needs of different people.
Or the one of the mystics, seeing all as God, and eventually allowing a sense of separate self to fall away.
The second part of the shahadan, wa muÄ§ammadan rasÅ«lu-llÄh, means that Muhammad is the messenger of Allah, and I can’t say I have any problems with that.
As a side-note: each of these have their own form of blasphemy as well. Within the ethnocentric interpretation, it is to worship or believe in any other God than the Islamic one. For the practitioner, it is to forget about God, or get absorbed into or intoxicated by anything else than God. For the worldcentric one, it is to deny anyone their religious freedom. And for the mystics, to worship the sense of a separate self. (Which is OK and just something to notice.)