The basic question is not about respecting cow, worshipping its rear or drinking its urine.
Its all about cow meat.
Sanatana dharma does not order you to follow a book or set of rules blindly. You will not be punished or thrown away or even killed for not going to a temple or not observing fast on ekadasi.
Basic idea is to question and extract logical answers.
Most of the scriptures are guru-sishya or siva-parvati conversation and questions keep coming until all are not answered.
Initial days even priests, rishis (read brahmins) were served meat but later they stopped as it was not required for their work. Also same rule was applied for traders, business communities as they have less physical work.
Others continued to eat meat as their work was more physical.
Then evolved the idea of not destroying a life completely for our food. If you take vegetavble or fruit from a plant/tree, its life is not finished.
The plant/tree still lives and gives more veg/fruits. The same idea applies to cow milk.
But when you want to eat chicken or goat meat, you have to end its life !
So the definition of vegetarian was defined on this principle. (does your food end a life or not).
Cow is a pet animal. It emotionally connects to the humans, especially to the family which feeds it.
That is why it lets only that family member to milk it regularly. One has to gain its trust to extract milk.
When a family member is sick or dies, you can observe what cow does. It cries and does not eat. It behaves like your family member.
Same is the case with your pet dog. They connect to their owners and families.
Meat or any food, when consumed tries to mix with human system. Any food has to mix and form a part of our own flesh. We get allergies when certain foods do not mix with our system.
Hen or goat do not connect to humans at that level, even is raised at home.
So their meat mixes with us after some struggle.
But pet animals are like family. Will you kill a family member and eat ?
Their meat struggles to mix with human system and this replusion causes diseases. This is what Ravana wrote about in his book 'Kumara Tantram' that beaf consumption leads to 93 types of diseases.
That is why Indians avoid meat of cow, dog etc.
Infact dog meat is avoided by most in the west too as its a pet animal.
Next thought came among vegetarians.
Plucking a veg/fruit from branches is okay but what about roots like carrot,onion,beetroot,ginger, potato ?
If you pluck these, life of that plant ends as you need to uproot them.
So jains and few hindus started avoiding any veg that is produced under the surface of earth, without sunrays contact.
cow dung, cow urine etc as medicine is another concept. Cow is the only animal which is useful to humans while alive and even after death. (skin, hoof are used and body buried in fileds).
All this is about desi cows with a hump which produce light yellow color milk. (not jersey cows)