A misconduct hearing held by South Yorkshire Police was told how Special Police Sergeant Adam Bayliss is accused of breaching the force's code of conduct through two comments posted on the internet on May 9 last year.
The first breach relates to a comment made by Mr Bayliss, who also works in the Environment Agency's contingency planning department, on the Bullshire Strikes Back Facebook group.
The group has almost 10,000 members and is dedicated to to addressing 'comments and behaviour which blame the Police for everything that goes wrong in the country'.
When questioned about the group and its users, Mr Bayliss agreed that it was mainly comprised of members of the police force and its supporters as well as people looking to 'troll' the police.
The comment in question was made on a thread about a police crash, the details from which were shared from a press release posted on the social media site by Northamptonshire Police.
On the thread, a woman posting on it had made fun of Mr Bayliss' profile picture, which was of his friend with ginger hair. The woman in question had made derogatory comments about the man's ginger hair.
In response Mr Bayliss made an offensive and inappropriate sexual comment about the woman, which also criticised her physical appearance and suggested she suffered from a deformity.
Giving evidence to yesterday's hearing, Mr Bayliss said: "[What she said] was about my friend, and I suppose that got to me a little bit.
"That doesn't excuse my actions. Reading that back, I'm really ashamed of myself."
He added: "I guess I was acting in a sense of misplaced loyalty to the police, which wasn't necessary."
The panel, comprised of senior police officers and independent members, was told how Mr Bayliss' comment was removed by Facebook and he was also given a 'strike' for breaching the social media site's community guidelines. Three such strikes would lead to him being banned from Facebook, the panel was told.
The woman's comment to Mr Bayliss was also removed by Facebook.
The second breach relates to a review Mr Bayliss made on the Facebook page of a company that had shared CCTV footage of a police crash near their premises.
After the company's post about the police crash was shared on the Bullshire Strikes Back group, Mr Bayliss left a negative review on their page. The review criticised the company for sharing the crash footage and stated that he would not being using their services again - despite never using them in the first place.
Asked why he used the word 'again', Mr Bayliss said he meant 'in the future'.
Mr Bayliss agreed that the comment inferred he had used the company's services, and as such, was misleading.
Following a day-long hearing, the panel found Mr Bayliss guilty of misconduct and served him with a first written warning that will stay on his record for 12 months.
Special police officers are members of the public who are required to complete at least 192 hours of volunteer work for the police every year. Mr Bayliss has been a special police officer since 2008, and the panel was told how on at least two of the years Mr Bayliss racked up over 1,000 hours of service to the police.