If you look, there is guidance for many professions about accessing public SM. Recruiters can leave themselves at risk of complaints about bias.
For example ACAS say.....
Under the General Data Protection Regulation (GDPR) employers must give job applicants certain information about how their personal data is collected and used. Commonly this is done via a privacy notice.
If social media screening forms part of the recruitment process, the privacy notice should make this clear (in the section outlining where personal information comes from); and set out the legal basis for processing the data. In this context the legal basis might be because it is necessary to enter into a contract; comply with a legal obligation; or for the employer's legitimate interests (e.g. to select suitable employees, workers or contractors).
If any of the data amounts to sensitive personal data (e.g. details of sexual orientation) then one of the additional processing conditions needs to be set out too, for example to exercise or perform employment law rights or obligations.
Screening candidates on social media can provide a host of information, for example regarding the candidate's age, ethnicity, religion, health, sexual orientation and family life. This is problematic for employers - the Equality Act 2010 makes it unlawful to discriminate against potential job candidates on the basis of these protected characteristics.
Acas warns that screening social media profiles can facilitate unconscious bias. For example, if an employer views a candidate's profile and becomes aware of, or has a perception of, their age or ethnicity for example, they might unknowingly form a judgement. If that person is not interviewed and they bring a discrimination claim, defending the claim becomes more difficult when their social media profile has been viewed. As the employer was aware of the candidate's protected characteristic it could be argued that this influenced the recruitment decision, even if it didn't.