Oppositional brand loyalty refers to consumers expressing loyalty to their preferred brand by opposing competing brands.Previous literature has mostly focused on the positive effects of oppositional brand loyalty on the preferred brand,with only a few scholars exploring the harm of oppositional brand loyalty to the preferred brand from a moral identity perspective.However,with the rapid development of online brand communities,immoral behavior towards competing brands in oppositional brand loyalty has become increasingly popular.Examples include trash-talking,schadenfreude,and malicious attacks.These oppositional brand loyalty behaviors may not only harm the preferred brand but also easily escalate into group confrontation and even trigger serious social problems.Existing research has pointed out that the aggressive behavior associated with oppositional brand loyalty can strengthen the positive attitudes of brand members,especially those with high brand identification.However,for the broader and larger group of bystanders and casual fans,will their attitudes be positively strengthened by the aggressive behavior of these brand members?Is it possible that their attitudes will become negative instead?Are casual fans considered part of the brand's internal group?Will their positive attitudes be similarly reinforced,like those of core fans,due to their engagement in attacking competing brands?The answers to these questions cannot be obtained from existing research,but it is important for brand managers to effectively manage fans and maintain brand competitive advantage by cultivating or strengthening consumers'oppositional brand loyalty.Therefore,this article integrates relevant theories on oppositional brand loyalty,trait transference,and attitude polarization.It explores the interactive effects of oppositional brand loyalty behaviors and brand users on brand attitude polarization through three experiments and investigates the underlying mechanisms.Experiment 1 adopts a between-subjects design of 2(oppositional brand loyalty:oppositional brand rejection vs.oppositional brand malice)x 3(brand users:enthusiastic users vs.utilitarian users vs.potential users).It chooses Real Madrid and Barcelona as experimental scenarios to explore the interactive effects of oppositional brand loyalty and brand user type on consumers'brand attitude polarization.Experiment 2 chooses Huawei and Apple as experimental scenarios to further verify the main effects and to explore the psychological mechanism of consumers'attitude polarization.Experiment 3 adopts a between-subjects design of 2(oppositional brand loyalty:oppositional brand rejection vs.oppositional brand malice)× 2(brand users:non-enthusiast vs.enthusiast).It chooses a celebrity as the brand scenario to verify the main effects and mediating mechanism.The results show that the hostile brand malice of brand enthusiasts(enthusiastic fans)would lead to negative polarization of brand attitudes among potential users(bystanders)and utilitarian users(casual fans).Additionally,trait transference plays a mediating role in the negative impact of these fans'behavior on the brand.This study has important theoretical implications.First,it reveals the double-edged sword effect of oppositional brand loyalty,especially its"dark side".Second,based on the trait transference theory,it explains the psychological mechanism by which oppositional brand loyalty leads to the polarization of consumers'brand attitudes.In addition to the above theoretical implications,this study is beneficial for both academia and industry to pay attention to and make good use of the positive effects of oppositional brand loyalty while also being aware of its potential negative consequences.Third,although oppositional brand loyalty can be effective,it also has the potential to create adverse social effects when fans attack others for selfish reasons.Enterprises need to play a proper leadership and should prevent fans from launching malicious attacks and exacerbating brand opposition for their own benefit.At the same time,the negative impact of fan behavior on brand reputation is no less than that of brand behavior,so brand or marketing personnel should have a dialectical view of the role of oppositional brand loyalty in the brand community.