White tips are much miligned and blamed for a lot that generally has nothing to do with them. There main goal is to eat black house spiders (which I like in the house) so I remove white tips to the garden. Been bitten by almost every type of Spider (Including white tips) but not Redbacks or a funnel web thankfully.
Flesh eating diseases are generally picked up from the garden - a scratch from a rose thorn can do it, but the victim then recalls seeing a white tip and the myth perpetuates.
White-tailed spider - Wikipedia - If you check out the study done it has a lot more detail, but couldn't immediately find it.