I appreciate their worry and grief. Believing and sharing "what they want to believe, need to believe" is NOT going to help bring him back. Facing, accepting and sharing facts, can.
(1) They say he would not leave...he did and did so, with a plan. He called in sick.
(2) They claim he would not go anywhere without telling them and saying when he would be back...he did. He went to the park. He stated he would be back in an hour when he couldn't possibly have been.
(3) They claim he would not leave of his free will - he did. LE confirmed this.
(4) They shared a picture of him - using your words and for example (not saying that is the reason they used this picture, so don't fly off the handle) - wanting/needing to believe he looks that way, is not going to make it so. If they share a picture of how he looks now, people are more likely to recognize him.
Emotions (fear, grief) are one thing. In order to solve this problem, the approach needs to be logical. The sooner he is found, the better the chance of him coming home safe.
With all due respect, I believe there are a lot of assumptions being made here. Maybe you're correct, but I can think of other reasons for the above which, in my opinion, are valid and worthy of consideration too.
Maybe he didn't leave with a plan. Is it possible he was actually feeling ill when he called in sick?
Could he have been car-jacked and forced to drive to that destination?
I know it was stated that he was not seen with another person, but could someone have been hidden in the car? Even have LE fooled?
Could he have been too frightened to say anything?
Could someone have threatened him
or​
his family if he didn't agree to their terms?
Are we certain beyond a doubt that he had control of his phone? Could it have been someone else, sending messages for him?
Could he have had an accident, even one near water, that has nothing to do with voluntarily leaving, or intentionally taking his own life?
You're entitled to your beliefs, and I'm not saying you're wrong. Chances are, in fact, that you're right.
But I see other possibilities. Not probabilities perhaps, but possibilities.
How can we really know for sure what happened?
In my opinion, his family is entitled to any feelings they have. They can say whatever they want, they can use any photo they want.
Honest, I'm not intending to come across as snarky at all. I know you're here because you care and want to help.
I'm just asking how can we hold up any reality mirrors for them when we don't know for certain, what that reality is?
JMO