Don't talk to him about politics because it's like a red rag to a bull..

فعلا تعبير جميل والمقصود من العبارة It's like a red rag to a bull ان الموضوع ده بيعصَّبُه وكتشبيه يعني بيخليه زي الطور اللي بيحطوا قدامه ملاية ولا ستارة حمرا بتخليه يتجنن ويهاجم اللي ماسكها يعني يتصادم مع الناس في الكلام.

احسنت مستر خالد اليك منى كل احترام وتقدير
a red rag to a bull
An object, utterance, or act which is certain to provoke someone:
the refusal to discuss the central issue was like a red rag to a bull

be like a red rag to a bull
if a statement or an action is like a red rag to a bull, it makes someone very angry
Usage notes: Some people believe that bulls become very angry when they see the colour red.

like a red rag to a bull
Definition: Something that will cause an angry or violent reaction.
A red rag to a bull is something - perhaps a comment or a criticism - intended to deliberately provoke someone else into reacting negatively. The expression may appear to have originated from bull-fighting, but this is not the case. There are, apparently, a large number of things that were believed to be distracted or angered by the waving of a red cloth, and the original expression, in fact, mentioned pheasants. Soon after came vipers, and then turkeys, and even Frenchmen! It wasn't until 1873 that bulls were added to the list. Strangely enough, bulls are in fact colour-blind, and therefore the colour of the rag is irrelevant. Nevertheless, the expression remains!
"Don't tell him you support Manchester United - it's like a red rag to a bull!"
"It was like a red rag to a bull when Samantha heard John say that men should be paid more than women."

be like a red rag to a bull
MAINLY UK
to be certain to produce an angry or violent reaction:
Don't tell him you're a vegetarian - it's like a red rag to a bull.

Origin
In the 17th century, to wave a red rag at someone was merely to chatter with them - 'red rag' was then a slang term for the tongue. This usage is cited in print as early as 1605 and is nicely illustrated in Francis Grose's definition in The
Classical Dictionary of the Vulgar Tongue, 1785:
"Shut your potatoe trap, and give your red rag a holiday."
The waving of a cloth rag at an animal to distract it may have been a common practice for centuries, but it wasn't until the 1700s that it was documented in print. The animal in question wasn't, as we might suppose, a bull. The first creature known to be susceptible to rag-waving was that most dim-witted of birds, the pheasant. This was cited in Trenchard and Gordon's religious essays, Cato's Letters, 1724:
Foxes are trapann'd [trapped] by Traces, Pheasants by a red Rag, and other Birds by a Whistle; and the same is true of Mankind.
Next come vipers, which were also thought to be adversely affected by red rags, as was recorded in The Times in March 1809:
"Truth to a lawyer was like a red rag to a viper - it extracted his venom."
Bulls come rather a long way down the list of red-rag-sensitive beings found in early citations. Before them we find turkeys and, not to be left out, Frenchmen - as in Catherine Gore's Memoires of a Peeress, 1837:
"They [the English] have no ardour for gratuitous quarrels; they do not fire up like a turkey-cock or a Frenchman, at sight of a red rag."
It wasn't until 1873 that someone decided that bulls were to be added to the list, when Charlotte Yonge included an allusion in the novel Pillars of the House:
"Jack will do for himself if he tells Wilmet her eyes are violet; it is like a red rag to a bull."
The inclusion of bulls on the list was rather misguided. Bulls don't have the optical equipment to distinguish red from other colours, so the 'red rag to a bull' phrase gives the wrong impression. It is generally accepted that bulls are enraged by the waving of the cloth rather than by its colour and that a green rag would work just as well. Personally, I've never been close enough to an annoyed bull for a double-blind trial, so to speak, and that's the way I prefer to keep it.