You see, this impacts them. Never mind that there's no actual impact, they only want those among them who behave as expected. Also, he got excessive attention due to his attire, which gave him a bigger audience for his political views.
Those who dismiss him because of his attire would, most likely, not listen to him, regardless. It's the others, who otherwise would know nothing of this man or his policies, who may be swayed in some way.
As someone who agrees with his dress style
It shows that he's young and different
And the uproar against his style made me interested in him as a person
*Btw this is the first time I've heard about it and strictly on first impressions