"only explaining what NARTH claims" no, it provides a soft endorsement. Wikipedia is for the benefit of readers, not for the progaganda interests of orgs.

The claim that all SSA treated by the org is "unwanted" is a WP:REDFLAG claim. 

See MOS:QUOTE - it is always wrong to use phrases like "The site is considered "sacred" by the religion's scriptures" because it interpolates an opinion - also WP:ATTRIBUTEPOV.

"no reason the lead shouldn't explain what NARTH's claims are" - WP:FRINGE and WP:REDFLAG applies - if they are wrong they need analysis in the body, not presentation as soft endorsement in the lead.