As far as the bold, that's not true.
Heat can cause scalp burns that lead to damage to the scalp and alopecia. If you ask a dermatologist they will tell you that much of the hair thinning/balding they see in black women as they age is due to scalp damage in the past from pressing combs and relaxers. The heat has just as much power to irreversibly damage hair follicles as a relaxer does.
Think of it this way, if you get a really bad burn on your arm, once a scar forms hair usually doesn't grow in that area anymore. The same thing happens on the scalp, especially since the skin there is much more sensitive.
I wish I could find the previous thread about it.
ETA: Here's the thread
http://www.longhaircareforum.com/showthread.php?t=328589.
And there's more about it if you google.
In general, I think black women need to take much much better care of their scalps. Whether it's slight tingling during a relaxer application, or a full on burn, or being burned with a pressing comb, flat iron, or hot hair grease, the scalp is taking a beating every time. Right underneath there are the hair follicles and they are taking just as much of a beating. You can't have healthy hair if your follicles are damaged...just something to think about.