So another thing to note here, is sometimes you don't want to, or cant start moving things around.

So with your example, you could cut the tube into 2 pieces (just before it starts to intersect) then union the 2 pieces together which will remove the intersecting surfaces and allow the Boolean to succeed.

Although, in this case, the intersection was so small and slivery, I had to do an interse3ction curves on the 2 pieces, then use "trim" to remove the little intersection surfaces and then join back to a solid and Boolean diff away from the block...

FYI.