Tauru was given a four-week ban at the VFL tribunal for rough conduct and it was upheld after the Saints appealed.
But with byes at the start and end of Tauru's four-week sanction, the 18-year-old is ineligible to play football for six weeks.
Lyon compared the penalty for St Kilda's first round draft pick to Richmond's Noah Balta, who was suspended for four matches as a result of the off-field incident that led to him being charged with assault.
"We're incredibly disappointed, I am really frustrated, it's a broken system," Lyon said on Wednesday.
"If you think the penalty is four weeks, that's OK, but they know we've got a bye and then at the end of that there's another bye."How the tribunal doesn't take into consideration that it's six weeks; Noah Balta got four weeks' stand-down for an assault off the field, with respect.
"We've got a kid that concussed a player, it's a six-week penalty, there's just no consideration - as Paul Roos would say 'common sense is commonly uncommon'."
In the spotlight last round for the spray he gave his players, most notably teenage midfielder Hugo Garcia, a still fired-up Lyon said AFL clubs would be better off running their own breakaway competition than fielding teams in the VFL.
"No wonder AFL clubs talk about 'Let's have a breakaway group from a 22-team competition and just have four or five clubs that play each other'," he said.
"It's not worth the risk and there's no recompense or consideration or adjustment for the reality of a misaligned fixture of a feeder competition to the AFL so I am absolutely filthy."What I would like is for common sense to prevail here for a young player.
"We talk about mental health ... the kid has been suspended for four and he'll miss six, how do you reckon his mental health is going at the minute? And mine."
