tar with the same brush

tar sb with the same brush
paint sb with the same brush
(to believe wrongly that someone or something has the same bad qualities as someone or something that is similar ) -- клеймить одним клеймом; всех под одну гребенку

be tarred with the same brush (as sb)
(to be thought to have the same faults, etc. as somebody else)

Related expressions
[под одну гребенку]
make sweeping generalizations