You are quite right - sin is sin and God hates sin…
While the Church has Mortal and venial this way…(From the CCC,
HERE)
1855 *Mortal sin *destroys charity in the heart of man by a grave violation of God’s law; it turns man away from God, who is his ultimate end and his beatitude, by preferring an inferior good to him.
Venial sin allows charity to subsist, even though it offends and wounds it
1856 Mortal sin, by attacking the vital principle within us - that is, charity - necessitates a new initiative of God’s mercy and a conversion of heart which is normally accomplished within the setting of the sacrament of reconciliation:
1857 For a sin to be mortal, three conditions must together be met: "Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent."131
1858 Grave matter is specified by the Ten Commandments, corresponding to the answer of Jesus to the rich young man: "Do not kill, Do not commit adultery, Do not steal, Do not bear false witness, Do not defraud, Honor your father and your mother."132 The gravity of sins is more or less great: murder is graver than theft. One must also take into account who is wronged: violence against parents is in itself graver than violence against a stranger.
1859 Mortal sin requires full knowledge and complete consent. It presupposes knowledge of the sinful character of the act, of its opposition to God’s law. It also implies a consent sufficiently deliberate to be a personal choice. Feigned ignorance and hardness of heart133 do not diminish, but rather increase, the voluntary character of a sin.
Now - in answer to your followup questions about “full knowledge, full consent and grave matter”…
I would explain it this way. Suppose a person converts at 30 years old. He has lived a fairly “normal” secular life with it’s normal sins and bad habits. The big ones like fornication, pornography, drunkeness he drops pretty readily. But some others, like cussing, foul language, glancing at a woman’s cleavage… are habits that takes him awhile to overcome. In general they are things that he knows are wrong and he tries not to do them but an occasional “d@mn” or f%#* slips out and he hasn’t quite trained his eyes yet to avoid looking at the female anatomy…
His intent is to NOT sin…He recognizes the sin immediately…He repents on the spot…
These are not sins of rejection or defiance but sins of habit that have not been subdued. So such sins would be venial and not mortal.
Hope this helps.
Peace
James