Just because a religion has people dying for it doesn't make it true.
It may be an indicator that there may be truth, or that the followers are seriously deluded.
There are religions that have followers committing ritual suicide, some that glorify death as a ultimate act of self-sacrifice and devotion.
I think that the argument that Christianity is true because people are willing to die for it isn't enough. We can look at followers of other religions that are willing to kill themselves (and perhaps others). Even even religion, look philosophies of thinking like the Kamikaze warriors of Japan who died for their country and their Emperor.
It isn't enough.
Christianity isn't true because other people died for it. It's true because Jesus died.
It isn't just dying. Dying is just an act. What is the meaning behind the act? Jesus died for what was right. There are people who died for what they believed was right in their own eyes. Jesus died in the face of suffering. That it was the facing the inevitable fact that life is suffering and the manner in which suffering must be faced. There is no such thing as a comfortable life. No person rich or poor can escape suffering in this world. Neither Bill Gates nor the poorest street urchin wandering the streets of Calcutta.
But then, just because a founder of a religion died, doesn't mean it's true either. Lots of people have died for the cause they founded, look at Gandhi, Martin Luther King.
So, therefore, the final thing that makes Christianity true is that Jesus rose from the dead.
That is the one thing that makes Christianity different. No other religion on earth, no philosophy can compare to that. It is the resurrection that makes everything different.