Remove the space padding margin around a ListViewItem

Would like to add style to the button, and don't understand why I have to include this line of code, where I don't want to add any Border to my button:

<Border Background="{TemplateBinding Background}">

The complete code:

<Style x:Key="ButtonStyleRed" TargetType="{x:Type Button}">
    <Setter Property="OverridesDefaultStyle" Value="True"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type Button}">
                <Border Background="{TemplateBinding Background}">
                    <StackPanel Orientation="Horizontal" Width="200">
                        <Rectangle Width="4" Height="30" Fill="#64dd17" Margin="0,0,10,1" RadiusX="2" RadiusY="2"/>
                        <TextBlock Text="{Binding Path=DataContext.FlowStageName,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Button}}}" 
                                   VerticalAlignment="Center" FontSize="14" Foreground="White" TextWrapping="WrapWithOverflow"/>
                    </StackPanel>
                 </Border>
                 <ControlTemplate.Triggers>
                    <Trigger Property="IsFocused" Value="True"/>
                    <Trigger Property="IsDefaulted" Value="True"/>
                    <Trigger Property="IsMouseOver" Value="True">
                        <Setter Property="Background" Value="#263238"></Setter>
                    </Trigger>
                    <Trigger Property="IsPressed" Value="True"/>
                    <Trigger Property="IsEnabled" Value="False"/>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="HorizontalAlignment" Value="Left"/>
    <Setter Property="Margin" Value="0"/>
    <Setter Property="Padding" Value="0"></Setter>
    <Setter Property="Width" Value="200"/>
    <Setter Property="Height" Value="50"/>
    <Setter Property="Background" Value="#37474f"/>
    <Setter Property="BorderThickness" Value="0"/>
</Style>

I would keep this like that but there are some other padding or margin issues which I can't resolved too.

When I don't have this border, Setter Property for Background color also doesn't work.

EDIT When I change it to below, it leave me with the padding/margin around the button. I have set Setters for Margin and Padding to 0, but this doesn't work.

<StackPanel Orientation="Horizontal" Width="200" Background="{TemplateBinding Background}" Margin="{TemplateBinding Padding}">
                      <Rectangle Width="4" Height="30" Fill="#64dd17" Margin="0,0,10,1" RadiusX="2" RadiusY="2"/>
                      <TextBlock Text="{Binding Path=DataContext.FlowStageName,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type Button}}}" 
                                   VerticalAlignment="Center" FontSize="14" Foreground="White" TextWrapping="WrapWithOverflow"/>
                 </StackPanel>

EDIT2

<views:BaseView.Resources>
    <views:SwapBooleanValueConverter x:Key="SwapBooleanValueConverter" />
    <DataTemplate x:Key="FlowStagesTemplate">
        <StackPanel>
            <Button x:Name="MenuStageButton"
                    Tag="{Binding ID}"
                    Command="{Binding DataContext.OnButtonClickCommand, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}" 
                    CommandParameter="{Binding ElementName=TurulStageButton}"
                    Style="{Binding FlowStageDisplayStyle}">
            </Button>
            <Rectangle VerticalAlignment="Stretch" Width="200" Margin="0" Height="1">
                <Rectangle.Fill>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,0" >
                        <GradientStop Color="#263238" Offset="0" />
                        <GradientStop Color="#78909c" Offset="0.5" />
                        <GradientStop Color="#263238" Offset="1.0" />
                    </LinearGradientBrush>
                </Rectangle.Fill>
            </Rectangle>
        </StackPanel>
    </DataTemplate>
</views:BaseView.Resources>
<StackPanel Background="#263238">
    <ListView ItemsSource="{Binding FlowStagesSubMenu}" ItemTemplate="{StaticResource FlowStagesTemplate}" 
              BorderThickness="0" Background="#263238" ScrollViewer.HorizontalScrollBarVisibility="Disabled" >
        <ListView.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Vertical"/>
            </ItemsPanelTemplate>
        </ListView.ItemsPanel>
    </ListView>
</StackPanel>