Like waving a red flag in front of a bull
Definition 1 of 1
Pro Tip 1/3Cultural Imagery
The phrase originates from bullfighting, where bulls react aggressively to the matador's red cape. 
His bright clothes at the funeral were like waving a red flag in front of a bull.
Pro Tip 2/3Confrontational Tone
Using this phrase suggests someone's actions are likely to cause an argument or upset someone. 
Complaining about the bonus was like waving a red flag in front of a bull.
Pro Tip 3/3Deliberate Provocation
The phrase emphasizes the intentionality behind the provocative action, knowingly causing a reaction. 
Mentioning politics at dinner was like waving a red flag in front of a bull.