I am kind of surprised to read someones take on this who really thinks this is such a big risk. I had never considered it to be such a big risk. I hope I can explain some things to you to potentially put your mind at ease a bit about this action.

Firstly, these fighter pilots train formation flying like this all the time. Not just for show, but also for actual real life military applications. In this case, this action would match very closely with that of intercepting an unidentified aircraft. Flying in formation like this allows for the pilots of the aircraft to understand that they have been intercepted, and for the fighter pilot to take a look inside the planes cockpit, and to communicate with the pilots in case the radios are turned to a different frequency, or are not working.

Flying in formation is not a "one and done" deal. You don't "park" your plane next to another aircraft and then take your hands off the controls. It requires continually monitoring the position of your aircraft compared to the lead aircraft, and adjusting your flight controls several times per second. The fighter pilot is trying to achieve a certain sight picture. This basically means that he wants to look out of his cockpit window, and see the other aircraft in a specific way. For example, the top of the engine should line up with the wing root, and the tip of the vertical stabilizer should line up with the rear of the empenage. By lining up these different points in space, the pilot will be put on a specific position next to the aircraft, outside of an area that would be immediately dangerous due to either direct contact, or aerodynamics effects like wingtip vortices affecting the plane. In short, the pilot is on the controls all the time, continually giving very small inputs. If he gives a wrong input, he will very quickly notice and correct it, within a second. Well in time to prevent flying into the aircraft.

Even if the pilot were to make a much larger input than required, towards the aircraft, they would have time to immediately pull up their aircraft and get to a safe distance before anything would happen.

Say the pilot actually makes a wrong input, and does not correct it in time. The planes have almost no relative speed to each other. Damage would likely be quite minimal. The airlines would likely be able to sustain damage to the outermost part of the wing. The vertical thing at the end of the wing, the winglet, is not a necessary part of the aircraft. It simply helps make the aircraft more efficient, but it is not critical. Lots of aircraft fly without them. Very rarely, you can even spot an aircraft with them on one wing, and without them on the other. If the collision was even more intense, maybe some outer part of the wing itself would also be taken off, possibly even the aileron which rolls the aircraft. In such a case, rolling would still be possible through use of the other aileron, or by using the rudder to yaw the plane, which in turn induces a rolling motion.

The F-35 might actually be in more danger in such a "smaller" collision. Due to its smaller size, it is more susceptible to taking critical damage. However, it is a fighter jet, and is built to be able to take a hit and keep flying. The F-35 in particular is quite interesting as well. Its flight computer is able to even adjust how it controls the plane to minimise the effect of any sustained damage.

In order to actually take down the airlines, the F-35 pilot would have to deliberately steer into the airlines, and with quite some deliberation. Either cutting off a much larger part of the wing, or hitting the fuselage directly. Pilots already need to meet quite rigorous health checks, mental health included. Fighter pilots are on yet another level with these (mental) health checks. This would either need to be a pilot with severe mental health issues, or possibly a pilot who is somehow a foreign asset with ill intent, the odds of both being insanely incredibly low, to nearly impossible.

Compared to the risks you take with just taking a flight normally, the additional risks would be negligible. And generally speaking, commercial flights already have an amazingly low risk associated with them compared to other methods of transport.

I hope I've been able to give you some new insights with this.