Well, if Protestants considered the early Christians as more Protestant than Catholic, then they might really consider themselves as having been accused of such. Anyway, I doubt if this is an issue among Protestants nowadays, except perhaps in discussions of early Church history.
Early Christians within the Roman Empire in the first and second centuries were accused of a lot of things owing to a malicious and prejudiced readings of early Christian practices. For example, pagans who heard that Christians shared the “Body and Blood” of Jesus in the Eucharist thought that it referred to actual human sacrifice and ritual cannibalism, while “love feasts” were mistaken for sexual orgies. By the third century, these rumours had been discredited as sheer fabrications.