An internet troll who posted nasty racist messages on Twitter has been jailed for six months.

Good. There are, sadly, many inadequate people who make spiteful, hate-filled comments on the internet that they would not have the courage to voice in person. They imagine that, because they post their remarks sitting in darkened rooms hunched over a computer screen, they have some sort of impunity. Well, thanks to the conviction of people like Michael Convery, perhaps it is dawning on these astonishingly slow learners that they do not.

Unfortunately, this latest incident targeting two Rangers players was no isolated case. Two other internet trolls were in the dock in London on Tuesday, pleading guilty to making menacing remarks including rape threats on Twitter to a feminist and a Labour MP. On Tuesday, a man who posted an online message about Celtic manager Neil Lennon including the line "I should've planned my parcel bombs better" was cleared of committing an offence because the sheriff did not consider that there was the necessary criminal intent required to convict. However Sheriff Stuart Reid did conclude that the comment had been "offensive and threatening". What all this shows is that internet "trolling", or making offensive comments or threats online, is prevalent.

This depressing phenomenon is not going to go away any time soon but it is essential that a culture does not develop where it is simply tolerated because of the mistaken notion that very little can be done about what people say online. It was worrying earlier this week to hear what sounded like echoes of that view coming from Justice Secretary Kenny MacAskill, who commented that enforcing the anonymity of people who had been arrested but not charged of an offence would be "pretty hard" because of social media. It may be true that it can be difficult to enforce the law in one legal jurisdiction on someone posting comments from another. Bringing the perpetrator to court in the victim's country would presumably depend on what sort of extradition arrangements existed between the two nations and whether the troll's identity could be established, but this scenario is the exception rather than the rule.

Where internet trolls are concerned, most seem to attack people close to home. In most cases the law can be enforced online. The Lord Advocate Frank Mulholland made this clear last month when he insisted a robust line be taken over hate comments about the Glasgow helicopter crash. About one dozen cases are being examined, some involving offensive, racist or sectarian comments.

This is not just a matter for police, lawmakers and prosecutors but any internet operator that allows comments to be made by members of the public on their site. They have a duty tightly to mediate these postings since an offensive remark does not have to be illegal to cause distress. Someone at a public meeting making vicious personal jibes would soon be ejected and exactly the same should apply to websites.

The internet is sometimes referred to as a modern Wild West, but even the Wild West was eventually tamed.