Taking Out The Trash Refutations
His instruction has one major problem - it has too many "holes" e.g. opponents moves which may take any >2000 player by surprise. For example after 3.Nxe5 he gives only 3...Qf6, ignoring moves which any White player must be aware - 3...Nc6 and 3...Nf6. White has advantage after these moves too, but - he must know how! Also after 1. e4 e5 2. Nf3 f5 3. Nxe5 Qf6 4. d4 d6 5. Nc4 fxe4 6. Nc3 Qg6 7. f3 he considers only 7...exf3, despite of fact that White must be prepared to play against 7...Nf6 and 7...Be7 too.
I would like to offer much safer and better way to play against Latvian, which was dissussed in chess.com forums too and recommended by IM pfren.