It is not a threat, it is by design. Do you really think Satoshi didn't know a few transactions per second are not enough to service all transactions done WW ? Scaling things is not a technological wonder. Especially in the digital domain. LN is a first solution and if needed others will be made. FUD will always exist, get used to it, beter counter them or help making solutions. Using Bitcoin on LN is factually a solution teach by example. Once you use it you will experience it is working fine not better way to explain.