Many Protestants are heretics, but not simply because they are Protestants. A Protestant is a heretic if he was a Catholic who embraced Protestant beliefs and practices. He selectively accepted some truths while rejecting others that the Catholic Church proposes as necessary for salvation. Many people still calling themselves Catholics are guilty of this too.
If he was himself a baptised Catholic who came to believe that (i.e., he refused to believe in the real presence) and then became a Protestant, yes he makes himself a heretic. But he was a heretic before he became Protestant because he refused to be corrected on the teaching (i.e., he obstinately denied post-baptism or obstinately doubted this truth which must be believed). Clearly, many modern Catholics fall into this camp while still referring to themselves as Catholics.
If he was born into a Protestant tradition or he became a Protestant without ever learning about the Catholic Church's teaching on the real presence, then no he cannot be a heretic. Someone who "denies" Church teaching without knowing it can't be a heretic. So, most Lutherans or Baptists or Anglicans or Pentecostals in 2025 aren't heretics because they weren't Catholic first and didn't know the Church's teaching and assent to it. The term "heretic" is loaded in our easily offended modern culture but it has a very precise meaning. Both Catholics and Protestants get it wrong all the time.
If a Protestant denies Christ present in the Eucharist, isn’t that heretical?
If he was himself a baptised Catholic who came to believe that (i.e., he refused to believe in the real presence) and then became a Protestant, yes he makes himself a heretic. But he was a heretic before he became Protestant because he refused to be corrected on the teaching (i.e., he obstinately denied post-baptism or obstinately doubted this truth which must be believed). Clearly, many modern Catholics fall into this camp while still referring to themselves as Catholics.
If he was born into a Protestant tradition or he became a Protestant without ever learning about the Catholic Church's teaching on the real presence, then no he cannot be a heretic. Someone who "denies" Church teaching without knowing it can't be a heretic. So, most Lutherans or Baptists or Anglicans or Pentecostals in 2025 aren't heretics because they weren't Catholic first and didn't know the Church's teaching and assent to it. The term "heretic" is loaded in our easily offended modern culture but it has a very precise meaning. Both Catholics and Protestants get it wrong all the time.