In a debate or argument, each side believes their argument is logical based on their own thinking. Really does anyone argue their view if they themselves believe it to be illogical? However, logic does not always equate with truthfulness. Let's look at a basic example:
A car has a long history of problems with the starter, only the starter.
Today the car does not start.
Conclusion: The starter must be malfunctioning again.
This is completely logical thinking. However, when the problem is looked into further, the truth is the battery is dead.
The point is, it is important to consider and accept all facts to come to both a logical and truthful conclusion. Therefore, stating something akin to "there is no need for data ... only logic" to support a stance, is untrue (and, in my thinking, illogical).