... and-- especially in the case of Catholic and Orthodox Christians -- they have added observances which clearly fall into the "which you have not known" category such as Trinity
On the most part, this is true, except, there are multiple definitions to the word, which upon inspection, one could still rightly apply, as witnessed in the TaNaKh. I agree that the word is not a great word, but considering what the TaNaKh does say first would be helpful, for instance:
Zec_13:7 Awake, O sword, against my shepherd, and against
the man that is my fellow, saith the LORD of hosts: smite the shepherd, and the sheep shall be scattered: and I will turn mine hand upon the little ones.
Isa_9:6 For unto us a child is born,
unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
Isa_48:16 Come ye near unto me, hear ye this; I have not spoken in secret from the beginning; from the time that it was, there am I: and now
the Lord GOD, and his Spirit, hath sent me.
Gen 19:24 Then
the LORD rained upon Sodom and upon Gomorrah brimstone and fire from
the LORD out of heaven;
Dan 7:13 I saw in the night visions, and, behold,
one like the Son of man came with the clouds of heaven, and came to the Ancient of days, and they brought him near before him.
Dan 7:14 And
there was given him dominion, and glory, and a kingdom, that all people, nations, and languages, should serve him: his dominion is an everlasting dominion, which shall not pass away, and his kingdom that which shall not be destroyed.
Zec 3:2 And
the LORD said unto Satan,
The LORD rebuke thee, O Satan; even
the LORD that hath chosen Jerusalem rebuke thee: is not this a brand plucked out of the fire?
Hos 1:4 And
the LORD said unto him, Call his name Jezreel; for yet a little while, and I will avenge the blood of Jezreel upon the house of Jehu, and will cause to cease the kingdom of the house of Israel.
Hos 1:5 And it shall come to pass at that day, that I will break the bow of Israel in the valley of Jezreel.
Hos 1:6 And she conceived again, and bare a daughter. And God said unto him, Call her name Loruhamah: for I will no more have mercy upon the house of Israel; but I will utterly take them away.
Hos 1:7 But
I will have mercy upon the house of Judah, and
will save them by the LORD their God, and will not save them by bow, nor by sword, nor by battle, by horses, nor by horsemen.
Pro 8:23
I was set up from everlasting, from the beginning, or ever the earth was.
Pro 8:27 When he prepared the heavens,
I was there: when he set a compass upon the face of the depth:
Pro 8:30 Then
I was by him, as
one brought up with him: and I was daily his delight, rejoicing always before him;
Ecc 12:1 Remember now thy
Creator in the days of thy youth, while the evil days come not, nor the years draw nigh, when thou shalt say, I have no pleasure in them;
(*plural Hebrew)
For, “Remember thy Creator in the days of thy youth,” is literally, “Remember thy Creators.” Again, “None saith, Where is God my Maker?” is in the Hebrew, “God my Makers.” So again, “Let Israel rejoice in him that made him,” is, in the Hebrew, “in his Makers.” And so again in the Proverbs, “The knowledge of the Holy Ones is understanding.” So again where the prophet says, “Thy Maker is thy husband,” both words are plural in the Hebrew. Many other passages of Scripture have precisely the same peculiarity.
And if you just want Torah, Genesis itself alone:
Gen 1:26 And God said, Let
us make man in
our image, after
our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.
Gen 3:22 And the LORD God said, Behold, the man is become as
one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
Exo_23:21 Beware of him, and obey his voice, provoke him not; for he will not pardon your transgressions: for
my name is in him.
etc.
... eating pig (which is big in the Bible Belt, even on the Day of Atonement), shellfish, etc. ...
Yeah, that is still a sin, not merely against God, for transgression of His law, but also against one's body, which belongs to God.
... (i.e. the ritual laws) ...
You will have to be more clear here, and give an example.
This one is a little more subil, since God is to be worshiped everyday, and at all times, and so, merely attending a service on "sunday" to worship God, wouldn't be transgression of any known law in scripture. However, to neglect the 4th commandment (Exodus 20:8-11) would be sin.
Yes, that is idolatry, etc and is sin, clearly forbidden in scripture. Jesus never taught that. Whenever Jesus is seen addressing Mary in scripture, it is "Woman".
... communion (drinking Jesus' blood and body) ...
Depends what you mean here definitionally. The Mass is blasphemy to be sure, and counter to all the scripture where it is forbidden to eat flesh of men, or drink any blood (men or not). However, since Jesus words were symbolic, those who just eat bread and drink the fruit of the vine (unfermented, no leaven) and dwell upon the words (bread) and life (blood) of Jesus transgress nothing written.
Joh_6:57
As the living Father hath sent me, and I live by the Father:
so he that eateth me, even he shall live by me.
The people in Jesus day, including His own disciples, were continually confusing the spiritual with the natural:
John 1:19-25 (John the Baptist as Elijah)
John 2:19-22 (Temple of His body)
John 3:1-21 (Nicodemus, Born Again)
John 4:7-15 (Woman a the Well, Water)
John 4:31-34 (Meat to Eat, Water to Drink)
John 5:6-7 (Will you be made whole, Pool)
John 6:50-52 (Eat my Flesh, Word)
John 7:38-39 (Water out of the belly, Spirit)
Matthew 16:5-12 (Leaven, Bread)
Jesus wasn't saying to take a bite out of Himself.
... infant baptism, etc.. ...
Agreed, there is no place in scripture which sanctions the pagan practice of infant baptism.
So, while there are such groups which do the things you mention, not all do. Therefore, why throw out the good with the bad?
I am Seventh-day Adventist.