"The statement is misleading because it mixes one true fact with an incorrect conclusion.

Here's how it actually works:

On most commercial aircraft, cabin air is indeed taken from the engine, but it is extracted from the compressor stage before fuel is burned. This air has not passed through the combustion chamber and is not exhaust gas.
The air is then cooled, conditioned, mixed with filtered recirculated cabin air, and distributed throughout the cabin.

So this claim:

"All of the air you're getting is mixed with monoxides and benzene from the engine."

is not accurate for normal aircraft operation.

There is, however, a related issue that sometimes causes confusion:

Aircraft can experience fume events, in which small amounts of engine oil or hydraulic fluid enter the bleed-air system because of a mechanical fault, such as a leaking seal. These events have been documented and are the subject of ongoing research.
A fume event is not the same thing as passengers continuously breathing engine exhaust.

If cabin air were routinely mixed with significant amounts of carbon monoxide or benzene from engine exhaust, it would pose an immediate and serious safety hazard for passengers and crew. The available evidence does not support that this occurs during normal commercial flights.

In short, the statement correctly notes that many aircraft use air supplied via the engines, but it incorrectly assumes that this means passengers are breathing engine exhaust. Those are two different things."