As I said in the other branch of the thread, I would expect a Muslim to find “Mohammed took some Nestorian heretical ideas and mixed them with some Jewish and Zoroastrian ideas to come up with Islam” offensive to the Prophet (given how it characterizes his sincerity by totally contradicting what he says about the origin of his message), in much the same way that I would expect a Lutheran to find disparagement of Luther’s sincerity offensive, or a Catholic to find disparagements of Mary’s sincerity offensive.
Likewise, Zachary’s comment in this branch that “they claim to believe in the God of Abraham, but I think that was just a stolen line to help break in Islam in the early years” questions the sincerity of the early Muslims’ belief that Allah is God of Abraham.
As for this being about Muslims4Lent, I would not say that it is really off topic, since that gesture is overtly ecumenical and representations of one faith by members of another do have a distinct impact upon interfaith relations. I would hope that it is possible for people of goodwill to discuss faith systems in which they themselves do not believe without needing to describe those faith systems as deliberate lies.