The acid in SLAs is dangerous stuff, the electrolyte in the various alkaline technology batteries is dangerous. If mis-treated, any battery will give you grief in return. A LiPo, properly treated, is no more dangerous than any other type, but, storing A LOT of energy in a small volume, will be more spectacular when it releases it all at once under failure conditions.
They are extensively used in consumer equipment, but use and charging is in conditions determined by the manufacturer of the equipment. When we use them, we are the manufacturer, and if we don't know the rules, we can have trouble.
The moral is - buy the proper gear for charging and using them - there isn't a safe, cheap alternative.