It's a well-intentioned comment that is actually true. However, it doesn't acknowledge the pain, suffering, and mourning of losing a loved one. If it is made before a person has a chance to grieve, it can be insensitive.
That wouldn't happen to me, as I had a plan B for my outdoor wedding. One always needs to have a plan B in case of rain/lightening!
If it is safe to be in that pavillion in the rain, lighteningwise, then I recommend you quickly make a lot of phone calls and see if you can get it tented.