But (I assume) you’re not a Muslim.
I believe that angles are sacred and should never be measured or calculated. The entire congregation of our church will now protest against the teaching of geometry and trigonometry outside Batley Grammar until they issue a full apology, remove maths and physics from the curriculum and sack all the teachers.
Freedom of religion is good. Everyone should be free to believe what they wish and worship accordingly, so long as it does not break any law (I have no issue with Satanism per se but don't agree with the child sacrifice bit) .
However, religion and state is segregated in all developed nations for a reason. No religion should be able to dictate what everyone else does and says.
Had this teacher taught the kids that Mohammed was a wanker that would have been wrong: because he's being paid to teach in a non-biased and constructive manner. However, from my understanding, this incident was in the context of a lesson on blasphemy - and the cartoon is very much in context.
The natural consequence of freedom to believe anything is the freedom to offend. Nobody has the right not to be offended, because that means that nobody is allowed to talk about whatever it is they believe... such as the Sacred Right Angle, The Holy Perpendicular. And that's especially true when some (a minority, not the people outside Batley Grammar) enforce their diktat with extreme violence.