Depending on which modpack you are using you might find it better to create an ME system using applied energistics as it gives more control.
The only way to solve this using logistics pipes is to make sure that the second crafting station is the lowest priority and have the iron blocks storage space as a higher priority.
priority list for pipe types.
High priority: Passive Supplier Modules
Normal priority: Basic Logistics Pipes and (Polymorphic) ItemSink Modules
Low priority: Terminus Modules
Lowest priority: Default routes provided by Basic Logistics Pipes and ItemSink Modules.
Your other option is to not have anywhere for iron ingots to go, this will mean that the crafting system will not craft them.
The crafting pipes are meant to be "Active requests" which means that they should only work when you request an item, so i would also check that you aren't actively requesting iron ingots anywhere.
Have a request logistics pipe, requesting the iron blocks to a specified location and none for iron ingots. then when you use the remote orderer to request iron ingots it should still work.
The issue occurs that i can't see your set up and there could be a number of reasons that your system is doing this. but hopefully these ideas help