You should not do anything that you are not assured in faith is not sin.
But some go by the tithe system and still use the Caesar deduction and that doesn’t make them out of the will of God since they come from the standpoint that Caesar is confidential and no glory comes to them personally thereby (the point of Jesus’ admonition, just like we don’t have to literally go into a closet for every prayer we pray).
Of course it doesn’t.
However, Cruz’s lack of a deduction on his taxes is hardly a reliable indicator of what the man actually tithes.
It’s a strawmans argument. There is not enough data to conclusively or reliably determine if he is or is not being charitable.
So why say such nonsense. It also does not change the fact that the man is a rock solid defender of Christian values and the constitution.