That's just silliness, I'd hardly hold that up as an example saying "this is how all Christians are."

First of all, I'd object to their tarnishing the senior picture with an "I [heart] Jesus" message, whether it said that or "I [heart] Britney Spears" or "I [heart] Bush" or "I [heart] Clinton".

It's just inappropriate, in any circumstance, in a formal high school class photo.
It's like if Bush showed up to give his State of the Union address in an "I [heart] Jesus" t-shirt. It would be a tacky representation of Jesus, and would also interfere with the dignity and ceremony of the event.
There is a time and place for political and religious statements, and a graduation photo is clearly not the time.
This is something you can be a Christian and still see as inappropriate. It's not fair to say that "this is how Christians are", or that "all Christians support this action." Or even "many Christians".

Secondly, "I [heart] Jesus" is hardly a message of conversion. It's not proselyizing, or in any way selling or teaching a Christian ideology, Any more than saying "I like Pepsi" is forcing my tastes on, or intimidating, anyone who doesn't like Pepsi.

The case of Roy Moore building a monument for the Ten Commandments is a different situation altogether.
Roy Moore is making a far more serious point, that the Ten Commandments, and the Bible itself, are the basis of American law, and for drafting of our Constitution and government, emulating the contract between God and Man, written in the Old and New Testaments.
Roy Moore's point goes beyond simple religious freedom, and makes a point about our heritage, and the ideals of those who signed the Declaration and Constitution.

And even so, Moore's Ten Commandments monument is NOT an attempt to hard-sell conversion to Christianity, but simply to acknowledge the source of our laws, and in doing so press our nation to have more conscience toward the purpose and standards of what the U.S. as a nation is about. In an era where our nation is increasingly compass-less.

Displaying the Quran in a police station is a considerably harder sell. And permitting it is a clear double-standard.