Liquid smoke is an interesting one. It seems like most of the really harmful compounds in smoke are fat soluble. Since liquid smoke is water-based, a lot of those compounds don't make it into the mix once everything is filtered.
It does contain small amounts of known carcinogens, but if you compare a teaspoon of your average liquid smoke product to say, smoked salmon, the liquid will be a tiny fraction of the safe limit while the salmon will tend to greatly exceed safe limits.
I'm not suggesting everyone should consume liquid smoke, and I agree, this is essentially junk food. You just put two question marks beside something I happen to know a bit about.
The main takeaway with smoked products is that they can be remarkably harmful to your health, with the exception of proper usage of liquid smoke. That can be hard to hear because good god, smoked food is delicious.
Smoked plant foods (i.e. tofu or tempeh) don't seem to carry nearly as much risk as smoked animal foods. I'm not sure why, but I think it is known.
This study is 30 years old, but offers some insight into risk factors for meats vs liquid smoke: https://pubmed.ncbi.nlm.nih.gov/8224319/
Since very small amounts of the liquid are used, one would end up ingesting ~1/40th or less of the carcinogenic compounds compares to if they, for example, ate a grilled pork chop.
> Total PAH concentrations in smoked meat products ranged from 2.6 micrograms/kg in a cooked ham sample to 29.8 micrograms/kg in grilled pork chops, while those in fish products ranged from 9.3 micrograms/kg in smoked shrimp to 86.6 micrograms/kg in smoked salmon.
Of course smoked salmon is the tastiest one on the list